ENH: support for `PySide6` in `%gui` (#13864)

Addresses  #13859

Changes here parallel the changes in
[ipykernel](https://github.com/ipython/ipykernel/pull/1054), i.e. prefer
`PyQt` over `PySide` and allow requesting explicit versions (e.g. 'qt5')
with one difference (see below).

I believe that, eventually, the Qt importing logic should be all here,
and `ipykernel` should defer to`ipython`. I chose not to do that at this
time since it would mean the latest `ipykernel` would require the latest
`IPython`; I'm happy to discuss further.

The only difference between `IPython` and `ipykernel`, after these two
pull requests, is that, in `IPython`, it's not possible to explicitly
request an event loop for Qt4. This is because an alias exists
[here](https://github.com/ipython/ipython/blob/5409de68d87ddd073a35111aca0cb8360ff63ca8/IPython/terminal/pt_inputhooks/__init__.py#L5)
which effectively makes "qt4" be "the latest Qt available". I did not
remove the alias because I don't know the history behind it.

IPython/terminal/tests/test_pt_inputhooks.py

@@ -0,0 +1,50 b''
+import os
+import importlib
+
+import pytest
+
+from IPython.terminal.pt_inputhooks import set_qt_api, get_inputhook_name_and_func
+
+
+guis_avail = []
+
+
+def _get_qt_vers():
+    """If any version of Qt is available, this will populate `guis_avail` with 'qt' and 'qtx'. Due
+    to the import mechanism, we can't import multiple versions of Qt in one session."""
+    for gui in ["qt", "qt6", "qt5"]:
+        print(f"Trying {gui}")
+        try:
+            set_qt_api(gui)
+            importlib.import_module("IPython.terminal.pt_inputhooks.qt")
+            guis_avail.append(gui)
+            if "QT_API" in os.environ.keys():
+                del os.environ["QT_API"]
+        except ImportError:
+            pass  # that version of Qt isn't available.
+        except RuntimeError:
+            pass  # the version of IPython doesn't know what to do with this Qt version.
+
+
+_get_qt_vers()
+
+
[e-mail](
+    len(guis_avail) == 0, reason="No viable version of PyQt or PySide installed."
+)
+def test_inputhook_qt():
+    gui = guis_avail[0]
+
+    # Choose a qt version and get the input hook function. This will import Qt...
+    get_inputhook_name_and_func(gui)
+
+    # ...and now we're stuck with this version of Qt for good; can't switch.
+    for not_gui in ["qt6", "qt5"]:
+        if not_gui not in guis_avail:
+            break
+
+    with pytest.raises(ImportError):
+        get_inputhook_name_and_func(not_gui)
+
+    # A gui of 'qt' means "best available", or in this case, the last one that was used.
+    get_inputhook_name_and_func("qt")

IPython/core/magics/basic.py

@@ -1,661 +1,663 b''
 """Implementation of basic magic functions."""
 
 
 from logging import error
 import io
 import os
 from pprint import pformat
 import sys
 from warnings import warn
 
 from traitlets.utils.importstring import import_item
 from IPython.core import magic_arguments, page
 from IPython.core.error import UsageError
 from IPython.core.magic import Magics, magics_class, line_magic, magic_escapes
 from IPython.utils.text import format_screen, dedent, indent
 from IPython.testing.skipdoctest import skip_doctest
 from IPython.utils.ipstruct import Struct
 
 
 class MagicsDisplay(object):
     def __init__(self, magics_manager, ignore=None):
         self.ignore = ignore if ignore else []
         self.magics_manager = magics_manager
     
     def _lsmagic(self):
         """The main implementation of the %lsmagic"""
         mesc = magic_escapes['line']
         cesc = magic_escapes['cell']
         mman = self.magics_manager
         magics = mman.lsmagic()
         out = ['Available line magics:',
                mesc + ('  '+mesc).join(sorted([m for m,v in magics['line'].items() if (v not in self.ignore)])),
                '',
                'Available cell magics:',
                cesc + ('  '+cesc).join(sorted([m for m,v in magics['cell'].items() if (v not in self.ignore)])),
                '',
                mman.auto_status()]
         return '\n'.join(out)
 
     def _repr_pretty_(self, p, cycle):
         p.text(self._lsmagic())
     
     def __str__(self):
         return self._lsmagic()
     
     def _jsonable(self):
         """turn magics dict into jsonable dict of the same structure
 
         replaces object instances with their class names as strings
         """
         magic_dict = {}
         mman = self.magics_manager
         magics = mman.lsmagic()
         for key, subdict in magics.items():
             d = {}
             magic_dict[key] = d
             for name, obj in subdict.items():
                 try:
                     classname = obj.__self__.__class__.__name__
                 except AttributeError:
                     classname = 'Other'
                 
                 d[name] = classname
         return magic_dict
         
     def _repr_json_(self):
         return self._jsonable()
 
 
 @magics_class
 class BasicMagics(Magics):
     """Magics that provide central IPython functionality.
 
     These are various magics that don't fit into specific categories but that
     are all part of the base 'IPython experience'."""
 
     @skip_doctest
     @magic_arguments.magic_arguments()
     @magic_arguments.argument(
         '-l', '--line', action='store_true',
         help="""Create a line magic alias."""
     )
     @magic_arguments.argument(
         '-c', '--cell', action='store_true',
         help="""Create a cell magic alias."""
     )
     @magic_arguments.argument(
         'name',
         help="""Name of the magic to be created."""
     )
     @magic_arguments.argument(
         'target',
         help="""Name of the existing line or cell magic."""
     )
     @magic_arguments.argument(
         '-p', '--params', default=None,
         help="""Parameters passed to the magic function."""
     )
     @line_magic
     def alias_magic(self, line=''):
         """Create an alias for an existing line or cell magic.
 
         Examples
         --------
         ::
 
           In [1]: %alias_magic t timeit
           Created `%t` as an alias for `%timeit`.
           Created `%%t` as an alias for `%%timeit`.
 
           In [2]: %t -n1 pass
           1 loops, best of 3: 954 ns per loop
 
           In [3]: %%t -n1
              ...: pass
              ...:
           1 loops, best of 3: 954 ns per loop
 
           In [4]: %alias_magic --cell whereami pwd
           UsageError: Cell magic function `%%pwd` not found.
           In [5]: %alias_magic --line whereami pwd
           Created `%whereami` as an alias for `%pwd`.
 
           In [6]: %whereami
           Out[6]: u'/home/testuser'
 
           In [7]: %alias_magic h history "-p -l 30" --line
           Created `%h` as an alias for `%history -l 30`.
         """
 
         args = magic_arguments.parse_argstring(self.alias_magic, line)
         shell = self.shell
         mman = self.shell.magics_manager
         escs = ''.join(magic_escapes.values())
 
         target = args.target.lstrip(escs)
         name = args.name.lstrip(escs)
 
         params = args.params
         if (params and
                 ((params.startswith('"') and params.endswith('"'))
                 or (params.startswith("'") and params.endswith("'")))):
             params = params[1:-1]
 
         # Find the requested magics.
         m_line = shell.find_magic(target, 'line')
         m_cell = shell.find_magic(target, 'cell')
         if args.line and m_line is None:
             raise UsageError('Line magic function `%s%s` not found.' %
                              (magic_escapes['line'], target))
         if args.cell and m_cell is None:
             raise UsageError('Cell magic function `%s%s` not found.' %
                              (magic_escapes['cell'], target))
 
         # If --line and --cell are not specified, default to the ones
         # that are available.
         if not args.line and not args.cell:
             if not m_line and not m_cell:
                 raise UsageError(
                     'No line or cell magic with name `%s` found.' % target
                 )
             args.line = bool(m_line)
             args.cell = bool(m_cell)
 
         params_str = "" if params is None else " " + params
 
         if args.line:
             mman.register_alias(name, target, 'line', params)
             print('Created `%s%s` as an alias for `%s%s%s`.' % (
                 magic_escapes['line'], name,
                 magic_escapes['line'], target, params_str))
 
         if args.cell:
             mman.register_alias(name, target, 'cell', params)
             print('Created `%s%s` as an alias for `%s%s%s`.' % (
                 magic_escapes['cell'], name,
                 magic_escapes['cell'], target, params_str))
 
     @line_magic
     def lsmagic(self, parameter_s=''):
         """List currently available magic functions."""
         return MagicsDisplay(self.shell.magics_manager, ignore=[])
 
     def _magic_docs(self, brief=False, rest=False):
         """Return docstrings from magic functions."""
         mman = self.shell.magics_manager
         docs = mman.lsmagic_docs(brief, missing='No documentation')
 
         if rest:
             format_string = '**%s%s**::\n\n%s\n\n'
         else:
             format_string = '%s%s:\n%s\n'
 
         return ''.join(
             [format_string % (magic_escapes['line'], fname,
                               indent(dedent(fndoc)))
              for fname, fndoc in sorted(docs['line'].items())]
             +
             [format_string % (magic_escapes['cell'], fname,
                               indent(dedent(fndoc)))
              for fname, fndoc in sorted(docs['cell'].items())]
         )
 
     @line_magic
     def magic(self, parameter_s=''):
         """Print information about the magic function system.
 
         Supported formats: -latex, -brief, -rest
         """
 
         mode = ''
         try:
             mode = parameter_s.split()[0][1:]
         except IndexError:
             pass
 
         brief = (mode == 'brief')
         rest = (mode == 'rest')
         magic_docs = self._magic_docs(brief, rest)
 
         if mode == 'latex':
             print(self.format_latex(magic_docs))
             return
         else:
             magic_docs = format_screen(magic_docs)
 
         out = ["""
 IPython's 'magic' functions
 ===========================
 
 The magic function system provides a series of functions which allow you to
 control the behavior of IPython itself, plus a lot of system-type
 features. There are two kinds of magics, line-oriented and cell-oriented.
 
 Line magics are prefixed with the % character and work much like OS
 command-line calls: they get as an argument the rest of the line, where
 arguments are passed without parentheses or quotes.  For example, this will
 time the given statement::
 
         %timeit range(1000)
 
 Cell magics are prefixed with a double %%, and they are functions that get as
 an argument not only the rest of the line, but also the lines below it in a
 separate argument.  These magics are called with two arguments: the rest of the
 call line and the body of the cell, consisting of the lines below the first.
 For example::
 
         %%timeit x = numpy.random.randn((100, 100))
         numpy.linalg.svd(x)
 
 will time the execution of the numpy svd routine, running the assignment of x
 as part of the setup phase, which is not timed.
 
 In a line-oriented client (the terminal or Qt console IPython), starting a new
 input with %% will automatically enter cell mode, and IPython will continue
 reading input until a blank line is given.  In the notebook, simply type the
 whole cell as one entity, but keep in mind that the %% escape can only be at
 the very start of the cell.
 
 NOTE: If you have 'automagic' enabled (via the command line option or with the
 %automagic function), you don't need to type in the % explicitly for line
 magics; cell magics always require an explicit '%%' escape.  By default,
 IPython ships with automagic on, so you should only rarely need the % escape.
 
 Example: typing '%cd mydir' (without the quotes) changes your working directory
 to 'mydir', if it exists.
 
 For a list of the available magic functions, use %lsmagic. For a description
 of any of them, type %magic_name?, e.g. '%cd?'.
 
 Currently the magic system has the following functions:""",
        magic_docs,
        "Summary of magic functions (from %slsmagic):" % magic_escapes['line'],
        str(self.lsmagic()),
        ]
         page.page('\n'.join(out))
 
 
     @line_magic
     def page(self, parameter_s=''):
         """Pretty print the object and display it through a pager.
 
         %page [options] OBJECT
 
         If no object is given, use _ (last output).
 
         Options:
 
           -r: page str(object), don't pretty-print it."""
 
         # After a function contributed by Olivier Aubert, slightly modified.
 
         # Process options/args
         opts, args = self.parse_options(parameter_s, 'r')
         raw = 'r' in opts
 
         oname = args and args or '_'
         info = self.shell._ofind(oname)
         if info['found']:
             if raw:
                 txt = str(info["obj"])
             else:
                 txt = pformat(info["obj"])
             page.page(txt)
         else:
             print('Object `%s` not found' % oname)
 
     @line_magic
     def pprint(self, parameter_s=''):
         """Toggle pretty printing on/off."""
         ptformatter = self.shell.display_formatter.formatters['text/plain']
         ptformatter.pprint = bool(1 - ptformatter.pprint)
         print('Pretty printing has been turned',
               ['OFF','ON'][ptformatter.pprint])
 
     @line_magic
     def colors(self, parameter_s=''):
         """Switch color scheme for prompts, info system and exception handlers.
 
         Currently implemented schemes: NoColor, Linux, LightBG.
 
         Color scheme names are not case-sensitive.
 
         Examples
         --------
         To get a plain black and white terminal::
 
           %colors nocolor
         """
         def color_switch_err(name):
             warn('Error changing %s color schemes.\n%s' %
                  (name, sys.exc_info()[1]), stacklevel=2)
 
 
         new_scheme = parameter_s.strip()
         if not new_scheme:
             raise UsageError(
                 "%colors: you must specify a color scheme. See '%colors?'")
         # local shortcut
         shell = self.shell
 
         # Set shell colour scheme
         try:
             shell.colors = new_scheme
             shell.refresh_style()
         except:
             color_switch_err('shell')
 
         # Set exception colors
         try:
             shell.InteractiveTB.set_colors(scheme = new_scheme)
             shell.SyntaxTB.set_colors(scheme = new_scheme)
         except:
             color_switch_err('exception')
 
         # Set info (for 'object?') colors
         if shell.color_info:
             try:
                 shell.inspector.set_active_scheme(new_scheme)
             except:
                 color_switch_err('object inspector')
         else:
             shell.inspector.set_active_scheme('NoColor')
 
     @line_magic
     def xmode(self, parameter_s=''):
         """Switch modes for the exception handlers.
 
         Valid modes: Plain, Context, Verbose, and Minimal.
 
         If called without arguments, acts as a toggle.
 
         When in verbose mode the value `--show` (and `--hide`)
         will respectively show (or hide) frames with ``__tracebackhide__ =
         True`` value set.
         """
 
         def xmode_switch_err(name):
             warn('Error changing %s exception modes.\n%s' %
                  (name,sys.exc_info()[1]))
 
         shell = self.shell
         if parameter_s.strip() == "--show":
             shell.InteractiveTB.skip_hidden = False
             return
         if parameter_s.strip() == "--hide":
             shell.InteractiveTB.skip_hidden = True
             return
 
         new_mode = parameter_s.strip().capitalize()
         try:
             shell.InteractiveTB.set_mode(mode=new_mode)
             print('Exception reporting mode:',shell.InteractiveTB.mode)
         except:
             xmode_switch_err('user')
 
     @line_magic
     def quickref(self, arg):
         """ Show a quick reference sheet """
         from IPython.core.usage import quick_reference
         qr = quick_reference + self._magic_docs(brief=True)
         page.page(qr)
 
     @line_magic
     def doctest_mode(self, parameter_s=''):
         """Toggle doctest mode on and off.
 
         This mode is intended to make IPython behave as much as possible like a
         plain Python shell, from the perspective of how its prompts, exceptions
         and output look.  This makes it easy to copy and paste parts of a
         session into doctests.  It does so by:
 
         - Changing the prompts to the classic ``>>>`` ones.
         - Changing the exception reporting mode to 'Plain'.
         - Disabling pretty-printing of output.
 
         Note that IPython also supports the pasting of code snippets that have
         leading '>>>' and '...' prompts in them.  This means that you can paste
         doctests from files or docstrings (even if they have leading
         whitespace), and the code will execute correctly.  You can then use
         '%history -t' to see the translated history; this will give you the
         input after removal of all the leading prompts and whitespace, which
         can be pasted back into an editor.
 
         With these features, you can switch into this mode easily whenever you
         need to do testing and changes to doctests, without having to leave
         your existing IPython session.
         """
 
         # Shorthands
         shell = self.shell
         meta = shell.meta
         disp_formatter = self.shell.display_formatter
         ptformatter = disp_formatter.formatters['text/plain']
         # dstore is a data store kept in the instance metadata bag to track any
         # changes we make, so we can undo them later.
         dstore = meta.setdefault('doctest_mode',Struct())
         save_dstore = dstore.setdefault
 
         # save a few values we'll need to recover later
         mode = save_dstore('mode',False)
         save_dstore('rc_pprint',ptformatter.pprint)
         save_dstore('xmode',shell.InteractiveTB.mode)
         save_dstore('rc_separate_out',shell.separate_out)
         save_dstore('rc_separate_out2',shell.separate_out2)
         save_dstore('rc_separate_in',shell.separate_in)
         save_dstore('rc_active_types',disp_formatter.active_types)
 
         if not mode:
             # turn on
 
             # Prompt separators like plain python
             shell.separate_in = ''
             shell.separate_out = ''
             shell.separate_out2 = ''
 
 
             ptformatter.pprint = False
             disp_formatter.active_types = ['text/plain']
 
             shell.magic('xmode Plain')
         else:
             # turn off
             shell.separate_in = dstore.rc_separate_in
 
             shell.separate_out = dstore.rc_separate_out
             shell.separate_out2 = dstore.rc_separate_out2
 
             ptformatter.pprint = dstore.rc_pprint
             disp_formatter.active_types = dstore.rc_active_types
 
             shell.magic('xmode ' + dstore.xmode)
 
         # mode here is the state before we switch; switch_doctest_mode takes
         # the mode we're switching to.
         shell.switch_doctest_mode(not mode)
 
         # Store new mode and inform
         dstore.mode = bool(not mode)
         mode_label = ['OFF','ON'][dstore.mode]
         print('Doctest mode is:', mode_label)
 
     @line_magic
     def gui(self, parameter_s=''):
         """Enable or disable IPython GUI event loop integration.
 
         %gui [GUINAME]
 
         This magic replaces IPython's threaded shells that were activated
         using the (pylab/wthread/etc.) command line flags.  GUI toolkits
         can now be enabled at runtime and keyboard
         interrupts should work without any problems.  The following toolkits
         are supported:  wxPython, PyQt4, PyGTK, Tk and Cocoa (OSX)::
 
             %gui wx      # enable wxPython event loop integration
-            %gui qt4|qt  # enable PyQt4 event loop integration
-            %gui qt5     # enable PyQt5 event loop integration
+            %gui qt      # enable PyQt/PySide event loop integration
+                         # with the latest version available.
+            %gui qt6     # enable PyQt6/PySide6 event loop integration
+            %gui qt5     # enable PyQt5/PySide2 event loop integration
             %gui gtk     # enable PyGTK event loop integration
             %gui gtk3    # enable Gtk3 event loop integration
             %gui gtk4    # enable Gtk4 event loop integration
             %gui tk      # enable Tk event loop integration
             %gui osx     # enable Cocoa event loop integration
                          # (requires %matplotlib 1.1)
             %gui         # disable all event loop integration
 
         WARNING:  after any of these has been called you can simply create
         an application object, but DO NOT start the event loop yourself, as
         we have already handled that.
         """
         opts, arg = self.parse_options(parameter_s, '')
         if arg=='': arg = None
         try:
             return self.shell.enable_gui(arg)
         except Exception as e:
             # print simple error message, rather than traceback if we can't
             # hook up the GUI
             error(str(e))
 
     @skip_doctest
     @line_magic
     def precision(self, s=''):
         """Set floating point precision for pretty printing.
 
         Can set either integer precision or a format string.
 
         If numpy has been imported and precision is an int,
         numpy display precision will also be set, via ``numpy.set_printoptions``.
 
         If no argument is given, defaults will be restored.
 
         Examples
         --------
         ::
 
             In [1]: from math import pi
 
             In [2]: %precision 3
             Out[2]: u'%.3f'
 
             In [3]: pi
             Out[3]: 3.142
 
             In [4]: %precision %i
             Out[4]: u'%i'
 
             In [5]: pi
             Out[5]: 3
 
             In [6]: %precision %e
             Out[6]: u'%e'
 
             In [7]: pi**10
             Out[7]: 9.364805e+04
 
             In [8]: %precision
             Out[8]: u'%r'
 
             In [9]: pi**10
             Out[9]: 93648.047476082982
         """
         ptformatter = self.shell.display_formatter.formatters['text/plain']
         ptformatter.float_precision = s
         return ptformatter.float_format
 
     @magic_arguments.magic_arguments()
     @magic_arguments.argument(
         'filename', type=str,
         help='Notebook name or filename'
     )
     @line_magic
     def notebook(self, s):
         """Export and convert IPython notebooks.
 
         This function can export the current IPython history to a notebook file.
         For example, to export the history to "foo.ipynb" do "%notebook foo.ipynb".
         """
         args = magic_arguments.parse_argstring(self.notebook, s)
         outfname = os.path.expanduser(args.filename)
 
         from nbformat import write, v4
 
         cells = []
         hist = list(self.shell.history_manager.get_range())
         if(len(hist)<=1):
             raise ValueError('History is empty, cannot export')
         for session, execution_count, source in hist[:-1]:
             cells.append(v4.new_code_cell(
                 execution_count=execution_count,
                 source=source
             ))
         nb = v4.new_notebook(cells=cells)
         with io.open(outfname, "w", encoding="utf-8") as f:
             write(nb, f, version=4)
 
 @magics_class
 class AsyncMagics(BasicMagics):
 
     @line_magic
     def autoawait(self, parameter_s):
         """
         Allow to change the status of the autoawait option.
 
         This allow you to set a specific asynchronous code runner.
 
         If no value is passed, print the currently used asynchronous integration
         and whether it is activated.
 
         It can take a number of value evaluated in the following order:
 
         - False/false/off deactivate autoawait integration
         - True/true/on activate autoawait integration using configured default
           loop
         - asyncio/curio/trio activate autoawait integration and use integration
           with said library.
 
         - `sync` turn on the pseudo-sync integration (mostly used for
           `IPython.embed()` which does not run IPython with a real eventloop and
           deactivate running asynchronous code. Turning on Asynchronous code with
           the pseudo sync loop is undefined behavior and may lead IPython to crash.
 
         If the passed parameter does not match any of the above and is a python
         identifier, get said object from user namespace and set it as the
         runner, and activate autoawait.
 
         If the object is a fully qualified object name, attempt to import it and
         set it as the runner, and activate autoawait.
 
         The exact behavior of autoawait is experimental and subject to change
         across version of IPython and Python.
         """
 
         param = parameter_s.strip()
         d = {True: "on", False: "off"}
 
         if not param:
             print("IPython autoawait is `{}`, and set to use `{}`".format(
                 d[self.shell.autoawait],
                 self.shell.loop_runner
             ))
             return None
 
         if param.lower() in ('false', 'off'):
             self.shell.autoawait = False
             return None
         if param.lower() in ('true', 'on'):
             self.shell.autoawait = True
             return None
 
         if param in self.shell.loop_runner_map:
             self.shell.loop_runner, self.shell.autoawait = self.shell.loop_runner_map[param]
             return None
 
         if param in self.shell.user_ns :
             self.shell.loop_runner = self.shell.user_ns[param]
             self.shell.autoawait = True
             return None
 
         runner = import_item(param)
 
         self.shell.loop_runner = runner
         self.shell.autoawait = True

IPython/external/qt_for_kernel.py

@@ -1,128 +1,124 b''
 """ Import Qt in a manner suitable for an IPython kernel.
 
 This is the import used for the `gui=qt` or `matplotlib=qt` initialization.
 
 Import Priority:
 
 if Qt has been imported anywhere else:
    use that
 
 if matplotlib has been imported and doesn't support v2 (<= 1.0.1):
     use PyQt4 @v1
 
 Next, ask QT_API env variable
 
 if QT_API not set:
     ask matplotlib what it's using. If Qt4Agg or Qt5Agg, then use the
         version matplotlib is configured with
 
     else: (matplotlib said nothing)
         # this is the default path - nobody told us anything
         try in this order:
             PyQt default version, PySide, PyQt5
 else:
     use what QT_API says
 
+    Note that %gui's implementation will always set a `QT_API`, see
+    `IPython.terminal.pt_inputhooks.get_inputhook_name_and_func`
+
 """
 # NOTE: This is no longer an external, third-party module, and should be
 # considered part of IPython. For compatibility however, it is being kept in
 # IPython/external.
 
 import os
 import sys
 
 from IPython.external.qt_loaders import (
     load_qt,
     loaded_api,
     enum_factory,
     # QT6
     QT_API_PYQT6,
     QT_API_PYSIDE6,
     # QT5
     QT_API_PYQT5,
     QT_API_PYSIDE2,
     # QT4
-    QT_API_PYQTv1,
     QT_API_PYQT,
     QT_API_PYSIDE,
     # default
     QT_API_PYQT_DEFAULT,
 )
 
 _qt_apis = (
     # QT6
     QT_API_PYQT6,
     QT_API_PYSIDE6,
     # QT5
     QT_API_PYQT5,
     QT_API_PYSIDE2,
-    # QT4
-    QT_API_PYQTv1,
-    QT_API_PYQT,
-    QT_API_PYSIDE,
     # default
     QT_API_PYQT_DEFAULT,
 )
 
 
 def matplotlib_options(mpl):
     """Constraints placed on an imported matplotlib."""
     if mpl is None:
         return
     backend = mpl.rcParams.get('backend', None)
     if backend == 'Qt4Agg':
         mpqt = mpl.rcParams.get('backend.qt4', None)
         if mpqt is None:
             return None
         if mpqt.lower() == 'pyside':
             return [QT_API_PYSIDE]
         elif mpqt.lower() == 'pyqt4':
             return [QT_API_PYQT_DEFAULT]
         elif mpqt.lower() == 'pyqt4v2':
             return [QT_API_PYQT]
         raise ImportError("unhandled value for backend.qt4 from matplotlib: %r" %
                           mpqt)
     elif backend == 'Qt5Agg':
         mpqt = mpl.rcParams.get('backend.qt5', None)
         if mpqt is None:
             return None
         if mpqt.lower() == 'pyqt5':
             return [QT_API_PYQT5]
         raise ImportError("unhandled value for backend.qt5 from matplotlib: %r" %
                           mpqt)
 
 def get_options():
     """Return a list of acceptable QT APIs, in decreasing order of preference."""
     #already imported Qt somewhere. Use that
     loaded = loaded_api()
     if loaded is not None:
         return [loaded]
 
-    mpl = sys.modules.get('matplotlib', None)
+    mpl = sys.modules.get("matplotlib", None)
 
     if mpl is not None and tuple(mpl.__version__.split(".")) < ("1", "0", "2"):
         # 1.0.1 only supports PyQt4 v1
         return [QT_API_PYQT_DEFAULT]
 
     qt_api = os.environ.get('QT_API', None)
     if qt_api is None:
         #no ETS variable. Ask mpl, then use default fallback path
         return matplotlib_options(mpl) or [
             QT_API_PYQT_DEFAULT,
             QT_API_PYQT6,
             QT_API_PYSIDE6,
             QT_API_PYQT5,
             QT_API_PYSIDE2,
-            QT_API_PYQT,
-            QT_API_PYSIDE,
         ]
     elif qt_api not in _qt_apis:
         raise RuntimeError("Invalid Qt API %r, valid values are: %r" %
                            (qt_api, ', '.join(_qt_apis)))
     else:
         return [qt_api]
 
 
 api_opts = get_options()
 QtCore, QtGui, QtSvg, QT_API = load_qt(api_opts)
 enum_helper = enum_factory(QT_API, QtCore)

IPython/external/qt_loaders.py

@@ -1,399 +1,405 b''
 """
 This module contains factory functions that attempt
 to return Qt submodules from the various python Qt bindings.
 
 It also protects against double-importing Qt with different
 bindings, which is unstable and likely to crash
 
 This is used primarily by qt and qt_for_kernel, and shouldn't
 be accessed directly from the outside
 """
 import importlib.abc
 import sys
 import types
 from functools import partial, lru_cache
 import operator
 
 # ### Available APIs.
 # Qt6
 QT_API_PYQT6 = "pyqt6"
 QT_API_PYSIDE6 = "pyside6"
 
 # Qt5
 QT_API_PYQT5 = 'pyqt5'
 QT_API_PYSIDE2 = 'pyside2'
 
 # Qt4
+# NOTE: Here for legacy matplotlib compatibility, but not really supported on the IPython side.
 QT_API_PYQT = "pyqt"  # Force version 2
 QT_API_PYQTv1 = "pyqtv1"  # Force version 2
 QT_API_PYSIDE = "pyside"
 
 QT_API_PYQT_DEFAULT = "pyqtdefault"  # use system default for version 1 vs. 2
 
 api_to_module = {
     # Qt6
     QT_API_PYQT6: "PyQt6",
     QT_API_PYSIDE6: "PySide6",
     # Qt5
     QT_API_PYQT5: "PyQt5",
     QT_API_PYSIDE2: "PySide2",
     # Qt4
     QT_API_PYSIDE: "PySide",
     QT_API_PYQT: "PyQt4",
     QT_API_PYQTv1: "PyQt4",
     # default
     QT_API_PYQT_DEFAULT: "PyQt6",
 }
 
 
 class ImportDenier(importlib.abc.MetaPathFinder):
     """Import Hook that will guard against bad Qt imports
     once IPython commits to a specific binding
     """
 
     def __init__(self):
         self.__forbidden = set()
 
     def forbid(self, module_name):
         sys.modules.pop(module_name, None)
         self.__forbidden.add(module_name)
 
     def find_spec(self, fullname, path, target=None):
         if path:
             return
         if fullname in self.__forbidden:
             raise ImportError(
                 """
     Importing %s disabled by IPython, which has
     already imported an Incompatible QT Binding: %s
     """
                 % (fullname, loaded_api())
             )
 
 
 ID = ImportDenier()
 sys.meta_path.insert(0, ID)
 
 
 def commit_api(api):
     """Commit to a particular API, and trigger ImportErrors on subsequent
     dangerous imports"""
     modules = set(api_to_module.values())
 
     modules.remove(api_to_module[api])
     for mod in modules:
         ID.forbid(mod)
 
 
 def loaded_api():
     """Return which API is loaded, if any
 
     If this returns anything besides None,
     importing any other Qt binding is unsafe.
 
     Returns
     -------
     None, 'pyside6', 'pyqt6', 'pyside2', 'pyside', 'pyqt', 'pyqt5', 'pyqtv1'
     """
     if sys.modules.get("PyQt6.QtCore"):
         return QT_API_PYQT6
     elif sys.modules.get("PySide6.QtCore"):
         return QT_API_PYSIDE6
     elif sys.modules.get("PyQt5.QtCore"):
         return QT_API_PYQT5
     elif sys.modules.get("PySide2.QtCore"):
         return QT_API_PYSIDE2
     elif sys.modules.get("PyQt4.QtCore"):
         if qtapi_version() == 2:
             return QT_API_PYQT
         else:
             return QT_API_PYQTv1
     elif sys.modules.get("PySide.QtCore"):
         return QT_API_PYSIDE
 
     return None
 
 
 def has_binding(api):
     """Safely check for PyQt4/5, PySide or PySide2, without importing submodules
 
     Parameters
     ----------
     api : str [ 'pyqtv1' | 'pyqt' | 'pyqt5' | 'pyside' | 'pyside2' | 'pyqtdefault']
         Which module to check for
 
     Returns
     -------
     True if the relevant module appears to be importable
     """
     module_name = api_to_module[api]
     from importlib.util import find_spec
 
     required = ['QtCore', 'QtGui', 'QtSvg']
     if api in (QT_API_PYQT5, QT_API_PYSIDE2, QT_API_PYQT6, QT_API_PYSIDE6):
         # QT5 requires QtWidgets too
         required.append('QtWidgets')
 
     for submod in required:
         try:
             spec = find_spec('%s.%s' % (module_name, submod))
         except ImportError:
             # Package (e.g. PyQt5) not found
             return False
         else:
             if spec is None:
                 # Submodule (e.g. PyQt5.QtCore) not found
                 return False
 
     if api == QT_API_PYSIDE:
         # We can also safely check PySide version
         import PySide
 
         return PySide.__version_info__ >= (1, 0, 3)
 
     return True
 
 
 def qtapi_version():
     """Return which QString API has been set, if any
 
     Returns
     -------
     The QString API version (1 or 2), or None if not set
     """
     try:
         import sip
     except ImportError:
         # as of PyQt5 5.11, sip is no longer available as a top-level
         # module and needs to be imported from the PyQt5 namespace
         try:
             from PyQt5 import sip
         except ImportError:
             return
     try:
         return sip.getapi('QString')
     except ValueError:
         return
 
 
 def can_import(api):
     """Safely query whether an API is importable, without importing it"""
     if not has_binding(api):
         return False
 
     current = loaded_api()
     if api == QT_API_PYQT_DEFAULT:
         return current in [QT_API_PYQT6, None]
     else:
         return current in [api, None]
 
 
 def import_pyqt4(version=2):
     """
     Import PyQt4
 
     Parameters
     ----------
     version : 1, 2, or None
         Which QString/QVariant API to use. Set to None to use the system
         default
     ImportErrors raised within this function are non-recoverable
     """
     # The new-style string API (version=2) automatically
     # converts QStrings to Unicode Python strings. Also, automatically unpacks
     # QVariants to their underlying objects.
     import sip
 
     if version is not None:
         sip.setapi('QString', version)
         sip.setapi('QVariant', version)
 
     from PyQt4 import QtGui, QtCore, QtSvg
 
     if QtCore.PYQT_VERSION < 0x040700:
         raise ImportError("IPython requires PyQt4 >= 4.7, found %s" %
                           QtCore.PYQT_VERSION_STR)
 
     # Alias PyQt-specific functions for PySide compatibility.
     QtCore.Signal = QtCore.pyqtSignal
     QtCore.Slot = QtCore.pyqtSlot
 
     # query for the API version (in case version == None)
     version = sip.getapi('QString')
     api = QT_API_PYQTv1 if version == 1 else QT_API_PYQT
     return QtCore, QtGui, QtSvg, api
 
 
 def import_pyqt5():
     """
     Import PyQt5
 
     ImportErrors raised within this function are non-recoverable
     """
 
     from PyQt5 import QtCore, QtSvg, QtWidgets, QtGui
 
     # Alias PyQt-specific functions for PySide compatibility.
     QtCore.Signal = QtCore.pyqtSignal
     QtCore.Slot = QtCore.pyqtSlot
 
     # Join QtGui and QtWidgets for Qt4 compatibility.
     QtGuiCompat = types.ModuleType('QtGuiCompat')
     QtGuiCompat.__dict__.update(QtGui.__dict__)
     QtGuiCompat.__dict__.update(QtWidgets.__dict__)
 
     api = QT_API_PYQT5
     return QtCore, QtGuiCompat, QtSvg, api
 
 
 def import_pyqt6():
     """
     Import PyQt6
 
     ImportErrors raised within this function are non-recoverable
     """
 
     from PyQt6 import QtCore, QtSvg, QtWidgets, QtGui
 
     # Alias PyQt-specific functions for PySide compatibility.
     QtCore.Signal = QtCore.pyqtSignal
     QtCore.Slot = QtCore.pyqtSlot
 
     # Join QtGui and QtWidgets for Qt4 compatibility.
     QtGuiCompat = types.ModuleType("QtGuiCompat")
     QtGuiCompat.__dict__.update(QtGui.__dict__)
     QtGuiCompat.__dict__.update(QtWidgets.__dict__)
 
     api = QT_API_PYQT6
     return QtCore, QtGuiCompat, QtSvg, api
 
 
 def import_pyside():
     """
     Import PySide
 
     ImportErrors raised within this function are non-recoverable
     """
     from PySide import QtGui, QtCore, QtSvg
     return QtCore, QtGui, QtSvg, QT_API_PYSIDE
 
 def import_pyside2():
     """
     Import PySide2
 
     ImportErrors raised within this function are non-recoverable
     """
     from PySide2 import QtGui, QtCore, QtSvg, QtWidgets, QtPrintSupport
 
     # Join QtGui and QtWidgets for Qt4 compatibility.
     QtGuiCompat = types.ModuleType('QtGuiCompat')
     QtGuiCompat.__dict__.update(QtGui.__dict__)
     QtGuiCompat.__dict__.update(QtWidgets.__dict__)
     QtGuiCompat.__dict__.update(QtPrintSupport.__dict__)
 
     return QtCore, QtGuiCompat, QtSvg, QT_API_PYSIDE2
 
 
 def import_pyside6():
     """
     Import PySide6
 
     ImportErrors raised within this function are non-recoverable
     """
     from PySide6 import QtGui, QtCore, QtSvg, QtWidgets, QtPrintSupport
 
     # Join QtGui and QtWidgets for Qt4 compatibility.
     QtGuiCompat = types.ModuleType("QtGuiCompat")
     QtGuiCompat.__dict__.update(QtGui.__dict__)
     QtGuiCompat.__dict__.update(QtWidgets.__dict__)
     QtGuiCompat.__dict__.update(QtPrintSupport.__dict__)
 
     return QtCore, QtGuiCompat, QtSvg, QT_API_PYSIDE6
 
 
 def load_qt(api_options):
     """
     Attempt to import Qt, given a preference list
     of permissible bindings
 
     It is safe to call this function multiple times.
 
     Parameters
     ----------
     api_options : List of strings
         The order of APIs to try. Valid items are 'pyside', 'pyside2',
         'pyqt', 'pyqt5', 'pyqtv1' and 'pyqtdefault'
 
     Returns
     -------
     A tuple of QtCore, QtGui, QtSvg, QT_API
     The first three are the Qt modules. The last is the
     string indicating which module was loaded.
 
     Raises
     ------
     ImportError, if it isn't possible to import any requested
     bindings (either because they aren't installed, or because
     an incompatible library has already been installed)
     """
     loaders = {
         # Qt6
         QT_API_PYQT6: import_pyqt6,
         QT_API_PYSIDE6: import_pyside6,
         # Qt5
         QT_API_PYQT5: import_pyqt5,
         QT_API_PYSIDE2: import_pyside2,
         # Qt4
         QT_API_PYSIDE: import_pyside,
         QT_API_PYQT: import_pyqt4,
         QT_API_PYQTv1: partial(import_pyqt4, version=1),
         # default
         QT_API_PYQT_DEFAULT: import_pyqt6,
     }
 
     for api in api_options:
 
         if api not in loaders:
             raise RuntimeError(
                 "Invalid Qt API %r, valid values are: %s" %
                 (api, ", ".join(["%r" % k for k in loaders.keys()])))
 
         if not can_import(api):
             continue
 
         #cannot safely recover from an ImportError during this
         result = loaders[api]()
         api = result[-1]  # changed if api = QT_API_PYQT_DEFAULT
         commit_api(api)
         return result
     else:
-        raise ImportError("""
+        raise ImportError(
+            """
     Could not load requested Qt binding. Please ensure that
-    PyQt4 >= 4.7, PyQt5, PySide >= 1.0.3 or PySide2 is available,
-    and only one is imported per session.
+    PyQt4 >= 4.7, PyQt5, PyQt6, PySide >= 1.0.3, PySide2, or
+    PySide6 is available, and only one is imported per session.
 
     Currently-imported Qt library:                              %r
-    PyQt4 available (requires QtCore, QtGui, QtSvg):            %s
     PyQt5 available (requires QtCore, QtGui, QtSvg, QtWidgets): %s
-    PySide >= 1.0.3 installed:                                  %s
+    PyQt6 available (requires QtCore, QtGui, QtSvg, QtWidgets): %s
     PySide2 installed:                                          %s
+    PySide6 installed:                                          %s
     Tried to load:                                              %r
-    """ % (loaded_api(),
-           has_binding(QT_API_PYQT),
-           has_binding(QT_API_PYQT5),
-           has_binding(QT_API_PYSIDE),
-           has_binding(QT_API_PYSIDE2),
-           api_options))
+    """
+            % (
+                loaded_api(),
+                has_binding(QT_API_PYQT5),
+                has_binding(QT_API_PYQT6),
+                has_binding(QT_API_PYSIDE2),
+                has_binding(QT_API_PYSIDE6),
+                api_options,
+            )
+        )
 
 
 def enum_factory(QT_API, QtCore):
     """Construct an enum helper to account for PyQt5 <-> PyQt6 changes."""
 
     @lru_cache(None)
     def _enum(name):
         # foo.bar.Enum.Entry (PyQt6) <=> foo.bar.Entry (non-PyQt6).
         return operator.attrgetter(
             name if QT_API == QT_API_PYQT6 else name.rpartition(".")[0]
         )(sys.modules[QtCore.__package__])
 
     return _enum

IPython/lib/guisupport.py

@@ -1,155 +1,155 b''
 # coding: utf-8
 """
 Support for creating GUI apps and starting event loops.
 
 IPython's GUI integration allows interactive plotting and GUI usage in IPython
 session. IPython has two different types of GUI integration:
 
 1. The terminal based IPython supports GUI event loops through Python's
    PyOS_InputHook. PyOS_InputHook is a hook that Python calls periodically
    whenever raw_input is waiting for a user to type code. We implement GUI
    support in the terminal by setting PyOS_InputHook to a function that
    iterates the event loop for a short while. It is important to note that
    in this situation, the real GUI event loop is NOT run in the normal
    manner, so you can't use the normal means to detect that it is running.
 2. In the two process IPython kernel/frontend, the GUI event loop is run in
    the kernel. In this case, the event loop is run in the normal manner by
    calling the function or method of the GUI toolkit that starts the event
    loop.
 
 In addition to starting the GUI event loops in one of these two ways, IPython
 will *always* create an appropriate GUI application object when GUi
 integration is enabled.
 
 If you want your GUI apps to run in IPython you need to do two things:
 
 1. Test to see if there is already an existing main application object. If
    there is, you should use it. If there is not an existing application object
    you should create one.
 2. Test to see if the GUI event loop is running. If it is, you should not
    start it. If the event loop is not running you may start it.
 
 This module contains functions for each toolkit that perform these things
 in a consistent manner. Because of how PyOS_InputHook runs the event loop
 you cannot detect if the event loop is running using the traditional calls
 (such as ``wx.GetApp.IsMainLoopRunning()`` in wxPython). If PyOS_InputHook is
 set These methods will return a false negative. That is, they will say the
 event loop is not running, when is actually is. To work around this limitation
 we proposed the following informal protocol:
 
 * Whenever someone starts the event loop, they *must* set the ``_in_event_loop``
   attribute of the main application object to ``True``. This should be done
   regardless of how the event loop is actually run.
 * Whenever someone stops the event loop, they *must* set the ``_in_event_loop``
   attribute of the main application object to ``False``.
 * If you want to see if the event loop is running, you *must* use ``hasattr``
   to see if ``_in_event_loop`` attribute has been set. If it is set, you
   *must* use its value. If it has not been set, you can query the toolkit
   in the normal manner.
 * If you want GUI support and no one else has created an application or
   started the event loop you *must* do this. We don't want projects to
   attempt to defer these things to someone else if they themselves need it.
 
 The functions below implement this logic for each GUI toolkit. If you need
 to create custom application subclasses, you will likely have to modify this
 code for your own purposes. This code can be copied into your own project
 so you don't have to depend on IPython.
 
 """
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 from IPython.core.getipython import get_ipython
 
 #-----------------------------------------------------------------------------
 # wx
 #-----------------------------------------------------------------------------
 
 def get_app_wx(*args, **kwargs):
     """Create a new wx app or return an exiting one."""
     import wx
     app = wx.GetApp()
     if app is None:
         if 'redirect' not in kwargs:
             kwargs['redirect'] = False
         app = wx.PySimpleApp(*args, **kwargs)
     return app
 
 def is_event_loop_running_wx(app=None):
     """Is the wx event loop running."""
     # New way: check attribute on shell instance
     ip = get_ipython()
     if ip is not None:
         if ip.active_eventloop and ip.active_eventloop == 'wx':
             return True
         # Fall through to checking the application, because Wx has a native way
         # to check if the event loop is running, unlike Qt.
 
     # Old way: check Wx application
     if app is None:
         app = get_app_wx()
     if hasattr(app, '_in_event_loop'):
         return app._in_event_loop
     else:
         return app.IsMainLoopRunning()
 
 def start_event_loop_wx(app=None):
     """Start the wx event loop in a consistent manner."""
     if app is None:
         app = get_app_wx()
     if not is_event_loop_running_wx(app):
         app._in_event_loop = True
         app.MainLoop()
         app._in_event_loop = False
     else:
         app._in_event_loop = True
 
 #-----------------------------------------------------------------------------
-# qt4
+# Qt
 #-----------------------------------------------------------------------------
 
 def get_app_qt4(*args, **kwargs):
-    """Create a new qt4 app or return an existing one."""
+    """Create a new Qt app or return an existing one."""
     from IPython.external.qt_for_kernel import QtGui
     app = QtGui.QApplication.instance()
     if app is None:
         if not args:
-            args = ([''],)
+            args = ([""],)
         app = QtGui.QApplication(*args, **kwargs)
     return app
 
 def is_event_loop_running_qt4(app=None):
-    """Is the qt4 event loop running."""
+    """Is the qt event loop running."""
     # New way: check attribute on shell instance
     ip = get_ipython()
     if ip is not None:
         return ip.active_eventloop and ip.active_eventloop.startswith('qt')
 
     # Old way: check attribute on QApplication singleton
     if app is None:
-        app = get_app_qt4([''])
+        app = get_app_qt4([""])
     if hasattr(app, '_in_event_loop'):
         return app._in_event_loop
     else:
-        # Does qt4 provide a other way to detect this?
+        # Does qt provide a other way to detect this?
         return False
 
 def start_event_loop_qt4(app=None):
-    """Start the qt4 event loop in a consistent manner."""
+    """Start the qt event loop in a consistent manner."""
     if app is None:
-        app = get_app_qt4([''])
+        app = get_app_qt4([""])
     if not is_event_loop_running_qt4(app):
         app._in_event_loop = True
         app.exec_()
         app._in_event_loop = False
     else:
         app._in_event_loop = True
 
 #-----------------------------------------------------------------------------
 # Tk
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # gtk
 #-----------------------------------------------------------------------------

IPython/terminal/interactiveshell.py

@@ -1,973 +1,978 b''
 """IPython terminal interface using prompt_toolkit"""
 
 import asyncio
 import os
 import sys
 from warnings import warn
 from typing import Union as UnionType
 
 from IPython.core.async_helpers import get_asyncio_loop
 from IPython.core.interactiveshell import InteractiveShell, InteractiveShellABC
 from IPython.utils.py3compat import input
 from IPython.utils.terminal import toggle_set_term_title, set_term_title, restore_term_title
 from IPython.utils.process import abbrev_cwd
 from traitlets import (
     Bool,
     Unicode,
     Dict,
     Integer,
     List,
     observe,
     Instance,
     Type,
     default,
     Enum,
     Union,
     Any,
     validate,
     Float,
 )
 
 from prompt_toolkit.auto_suggest import AutoSuggestFromHistory
 from prompt_toolkit.enums import DEFAULT_BUFFER, EditingMode
 from prompt_toolkit.filters import HasFocus, Condition, IsDone
 from prompt_toolkit.formatted_text import PygmentsTokens
 from prompt_toolkit.history import History
 from prompt_toolkit.layout.processors import ConditionalProcessor, HighlightMatchingBracketProcessor
 from prompt_toolkit.output import ColorDepth
 from prompt_toolkit.patch_stdout import patch_stdout
 from prompt_toolkit.shortcuts import PromptSession, CompleteStyle, print_formatted_text
 from prompt_toolkit.styles import DynamicStyle, merge_styles
 from prompt_toolkit.styles.pygments import style_from_pygments_cls, style_from_pygments_dict
 from prompt_toolkit import __version__ as ptk_version
 
 from pygments.styles import get_style_by_name
 from pygments.style import Style
 from pygments.token import Token
 
 from .debugger import TerminalPdb, Pdb
 from .magics import TerminalMagics
 from .pt_inputhooks import get_inputhook_name_and_func
 from .prompts import Prompts, ClassicPrompts, RichPromptDisplayHook
 from .ptutils import IPythonPTCompleter, IPythonPTLexer
 from .shortcuts import (
     create_ipython_shortcuts,
     create_identifier,
     RuntimeBinding,
     add_binding,
 )
 from .shortcuts.filters import KEYBINDING_FILTERS, filter_from_string
 from .shortcuts.auto_suggest import (
     NavigableAutoSuggestFromHistory,
     AppendAutoSuggestionInAnyLine,
 )
 
 PTK3 = ptk_version.startswith('3.')
 
 
 class _NoStyle(Style): pass
 
 
 
 _style_overrides_light_bg = {
             Token.Prompt: '#ansibrightblue',
             Token.PromptNum: '#ansiblue bold',
             Token.OutPrompt: '#ansibrightred',
             Token.OutPromptNum: '#ansired bold',
 }
 
 _style_overrides_linux = {
             Token.Prompt: '#ansibrightgreen',
             Token.PromptNum: '#ansigreen bold',
             Token.OutPrompt: '#ansibrightred',
             Token.OutPromptNum: '#ansired bold',
 }
 
 def get_default_editor():
     try:
         return os.environ['EDITOR']
     except KeyError:
         pass
     except UnicodeError:
         warn("$EDITOR environment variable is not pure ASCII. Using platform "
              "default editor.")
 
     if os.name == 'posix':
         return 'vi'  # the only one guaranteed to be there!
     else:
         return 'notepad' # same in Windows!
 
 # conservatively check for tty
 # overridden streams can result in things like:
 # - sys.stdin = None
 # - no isatty method
 for _name in ('stdin', 'stdout', 'stderr'):
     _stream = getattr(sys, _name)
     try:
         if not _stream or not hasattr(_stream, "isatty") or not _stream.isatty():
             _is_tty = False
             break
     except ValueError:
         # stream is closed
         _is_tty = False
         break
 else:
     _is_tty = True
 
 
 _use_simple_prompt = ('IPY_TEST_SIMPLE_PROMPT' in os.environ) or (not _is_tty)
 
 def black_reformat_handler(text_before_cursor):
     """
     We do not need to protect against error,
     this is taken care at a higher level where any reformat error is ignored.
     Indeed we may call reformatting on incomplete code.
     """
     import black
 
     formatted_text = black.format_str(text_before_cursor, mode=black.FileMode())
     if not text_before_cursor.endswith("\n") and formatted_text.endswith("\n"):
         formatted_text = formatted_text[:-1]
     return formatted_text
 
 
 def yapf_reformat_handler(text_before_cursor):
     from yapf.yapflib import file_resources
     from yapf.yapflib import yapf_api
 
     style_config = file_resources.GetDefaultStyleForDir(os.getcwd())
     formatted_text, was_formatted = yapf_api.FormatCode(
         text_before_cursor, style_config=style_config
     )
     if was_formatted:
         if not text_before_cursor.endswith("\n") and formatted_text.endswith("\n"):
             formatted_text = formatted_text[:-1]
         return formatted_text
     else:
         return text_before_cursor
 
 
 class PtkHistoryAdapter(History):
     """
     Prompt toolkit has it's own way of handling history, Where it assumes it can
     Push/pull from history.
 
     """
 
     def __init__(self, shell):
         super().__init__()
         self.shell = shell
         self._refresh()
 
     def append_string(self, string):
         # we rely on sql for that.
         self._loaded = False
         self._refresh()
 
     def _refresh(self):
         if not self._loaded:
             self._loaded_strings = list(self.load_history_strings())
 
     def load_history_strings(self):
         last_cell = ""
         res = []
         for __, ___, cell in self.shell.history_manager.get_tail(
             self.shell.history_load_length, include_latest=True
         ):
             # Ignore blank lines and consecutive duplicates
             cell = cell.rstrip()
             if cell and (cell != last_cell):
                 res.append(cell)
                 last_cell = cell
         yield from res[::-1]
 
     def store_string(self, string: str) -> None:
         pass
 
 class TerminalInteractiveShell(InteractiveShell):
     mime_renderers = Dict().tag(config=True)
 
     space_for_menu = Integer(6, help='Number of line at the bottom of the screen '
                                      'to reserve for the tab completion menu, '
                                      'search history, ...etc, the height of '
                                      'these menus will at most this value. '
                                      'Increase it is you prefer long and skinny '
                                      'menus, decrease for short and wide.'
                             ).tag(config=True)
 
     pt_app: UnionType[PromptSession, None] = None
     auto_suggest: UnionType[
         AutoSuggestFromHistory, NavigableAutoSuggestFromHistory, None
     ] = None
     debugger_history = None
 
     debugger_history_file = Unicode(
         "~/.pdbhistory", help="File in which to store and read history"
     ).tag(config=True)
 
     simple_prompt = Bool(_use_simple_prompt,
         help="""Use `raw_input` for the REPL, without completion and prompt colors.
 
             Useful when controlling IPython as a subprocess, and piping STDIN/OUT/ERR. Known usage are:
             IPython own testing machinery, and emacs inferior-shell integration through elpy.
 
             This mode default to `True` if the `IPY_TEST_SIMPLE_PROMPT`
             environment variable is set, or the current terminal is not a tty."""
             ).tag(config=True)
 
     @property
     def debugger_cls(self):
         return Pdb if self.simple_prompt else TerminalPdb
 
     confirm_exit = Bool(True,
         help="""
         Set to confirm when you try to exit IPython with an EOF (Control-D
         in Unix, Control-Z/Enter in Windows). By typing 'exit' or 'quit',
         you can force a direct exit without any confirmation.""",
     ).tag(config=True)
 
     editing_mode = Unicode('emacs',
         help="Shortcut style to use at the prompt. 'vi' or 'emacs'.",
     ).tag(config=True)
 
     emacs_bindings_in_vi_insert_mode = Bool(
         True,
         help="Add shortcuts from 'emacs' insert mode to 'vi' insert mode.",
     ).tag(config=True)
 
     modal_cursor = Bool(
         True,
         help="""
        Cursor shape changes depending on vi mode: beam in vi insert mode,
        block in nav mode, underscore in replace mode.""",
     ).tag(config=True)
 
     ttimeoutlen = Float(
         0.01,
         help="""The time in milliseconds that is waited for a key code
        to complete.""",
     ).tag(config=True)
 
     timeoutlen = Float(
         0.5,
         help="""The time in milliseconds that is waited for a mapped key
        sequence to complete.""",
     ).tag(config=True)
 
     autoformatter = Unicode(
         None,
         help="Autoformatter to reformat Terminal code. Can be `'black'`, `'yapf'` or `None`",
         allow_none=True
     ).tag(config=True)
 
     auto_match = Bool(
         False,
         help="""
         Automatically add/delete closing bracket or quote when opening bracket or quote is entered/deleted.
         Brackets: (), [], {}
         Quotes: '', \"\"
         """,
     ).tag(config=True)
 
     mouse_support = Bool(False,
         help="Enable mouse support in the prompt\n(Note: prevents selecting text with the mouse)"
     ).tag(config=True)
 
     # We don't load the list of styles for the help string, because loading
     # Pygments plugins takes time and can cause unexpected errors.
     highlighting_style = Union([Unicode('legacy'), Type(klass=Style)],
         help="""The name or class of a Pygments style to use for syntax
         highlighting. To see available styles, run `pygmentize -L styles`."""
     ).tag(config=True)
 
     @validate('editing_mode')
     def _validate_editing_mode(self, proposal):
         if proposal['value'].lower() == 'vim':
             proposal['value']= 'vi'
         elif proposal['value'].lower() == 'default':
             proposal['value']= 'emacs'
 
         if hasattr(EditingMode, proposal['value'].upper()):
             return proposal['value'].lower()
 
         return self.editing_mode
 
 
     @observe('editing_mode')
     def _editing_mode(self, change):
         if self.pt_app:
             self.pt_app.editing_mode = getattr(EditingMode, change.new.upper())
 
     def _set_formatter(self, formatter):
         if formatter is None:
             self.reformat_handler = lambda x:x
         elif formatter == 'black':
             self.reformat_handler = black_reformat_handler
         elif formatter == "yapf":
             self.reformat_handler = yapf_reformat_handler
         else:
             raise ValueError
 
     @observe("autoformatter")
     def _autoformatter_changed(self, change):
         formatter = change.new
         self._set_formatter(formatter)
 
     @observe('highlighting_style')
     @observe('colors')
     def _highlighting_style_changed(self, change):
         self.refresh_style()
 
     def refresh_style(self):
         self._style = self._make_style_from_name_or_cls(self.highlighting_style)
 
 
     highlighting_style_overrides = Dict(
         help="Override highlighting format for specific tokens"
     ).tag(config=True)
 
     true_color = Bool(False,
         help="""Use 24bit colors instead of 256 colors in prompt highlighting.
         If your terminal supports true color, the following command should
         print ``TRUECOLOR`` in orange::
 
             printf \"\\x1b[38;2;255;100;0mTRUECOLOR\\x1b[0m\\n\"
         """,
     ).tag(config=True)
 
     editor = Unicode(get_default_editor(),
         help="Set the editor used by IPython (default to $EDITOR/vi/notepad)."
     ).tag(config=True)
 
     prompts_class = Type(Prompts, help='Class used to generate Prompt token for prompt_toolkit').tag(config=True)
 
     prompts = Instance(Prompts)
 
     @default('prompts')
     def _prompts_default(self):
         return self.prompts_class(self)
 
 #    @observe('prompts')
 #    def _(self, change):
 #        self._update_layout()
 
     @default('displayhook_class')
     def _displayhook_class_default(self):
         return RichPromptDisplayHook
 
     term_title = Bool(True,
         help="Automatically set the terminal title"
     ).tag(config=True)
 
     term_title_format = Unicode("IPython: {cwd}",
         help="Customize the terminal title format.  This is a python format string. " +
              "Available substitutions are: {cwd}."
     ).tag(config=True)
 
     display_completions = Enum(('column', 'multicolumn','readlinelike'),
         help= ( "Options for displaying tab completions, 'column', 'multicolumn', and "
                 "'readlinelike'. These options are for `prompt_toolkit`, see "
                 "`prompt_toolkit` documentation for more information."
                 ),
         default_value='multicolumn').tag(config=True)
 
     highlight_matching_brackets = Bool(True,
         help="Highlight matching brackets.",
     ).tag(config=True)
 
     extra_open_editor_shortcuts = Bool(False,
         help="Enable vi (v) or Emacs (C-X C-E) shortcuts to open an external editor. "
              "This is in addition to the F2 binding, which is always enabled."
     ).tag(config=True)
 
     handle_return = Any(None,
         help="Provide an alternative handler to be called when the user presses "
              "Return. This is an advanced option intended for debugging, which "
              "may be changed or removed in later releases."
     ).tag(config=True)
 
     enable_history_search = Bool(True,
         help="Allows to enable/disable the prompt toolkit history search"
     ).tag(config=True)
 
     autosuggestions_provider = Unicode(
         "NavigableAutoSuggestFromHistory",
         help="Specifies from which source automatic suggestions are provided. "
         "Can be set to ``'NavigableAutoSuggestFromHistory'`` (:kbd:`up` and "
         ":kbd:`down` swap suggestions), ``'AutoSuggestFromHistory'``, "
         " or ``None`` to disable automatic suggestions. "
         "Default is `'NavigableAutoSuggestFromHistory`'.",
         allow_none=True,
     ).tag(config=True)
 
     def _set_autosuggestions(self, provider):
         # disconnect old handler
         if self.auto_suggest and isinstance(
             self.auto_suggest, NavigableAutoSuggestFromHistory
         ):
             self.auto_suggest.disconnect()
         if provider is None:
             self.auto_suggest = None
         elif provider == "AutoSuggestFromHistory":
             self.auto_suggest = AutoSuggestFromHistory()
         elif provider == "NavigableAutoSuggestFromHistory":
             self.auto_suggest = NavigableAutoSuggestFromHistory()
         else:
             raise ValueError("No valid provider.")
         if self.pt_app:
             self.pt_app.auto_suggest = self.auto_suggest
 
     @observe("autosuggestions_provider")
     def _autosuggestions_provider_changed(self, change):
         provider = change.new
         self._set_autosuggestions(provider)
 
     shortcuts = List(
         trait=Dict(
             key_trait=Enum(
                 [
                     "command",
                     "match_keys",
                     "match_filter",
                     "new_keys",
                     "new_filter",
                     "create",
                 ]
             ),
             per_key_traits={
                 "command": Unicode(),
                 "match_keys": List(Unicode()),
                 "match_filter": Unicode(),
                 "new_keys": List(Unicode()),
                 "new_filter": Unicode(),
                 "create": Bool(False),
             },
         ),
         help="""Add, disable or modifying shortcuts.
 
         Each entry on the list should be a dictionary with ``command`` key
         identifying the target function executed by the shortcut and at least
         one of the following:
 
         - ``match_keys``: list of keys used to match an existing shortcut,
         - ``match_filter``: shortcut filter used to match an existing shortcut,
         - ``new_keys``: list of keys to set,
         - ``new_filter``: a new shortcut filter to set
 
         The filters have to be composed of pre-defined verbs and joined by one
         of the following conjunctions: ``&`` (and), ``|`` (or), ``~`` (not).
         The pre-defined verbs are:
 
         {}
 
 
         To disable a shortcut set ``new_keys`` to an empty list.
         To add a shortcut add key ``create`` with value ``True``.
 
         When modifying/disabling shortcuts, ``match_keys``/``match_filter`` can
         be omitted if the provided specification uniquely identifies a shortcut
         to be modified/disabled. When modifying a shortcut ``new_filter`` or
         ``new_keys`` can be omitted which will result in reuse of the existing
         filter/keys.
 
         Only shortcuts defined in IPython (and not default prompt-toolkit
         shortcuts) can be modified or disabled. The full list of shortcuts,
         command identifiers and filters is available under
         :ref:`terminal-shortcuts-list`.
         """.format(
             "\n        ".join([f"- `{k}`" for k in KEYBINDING_FILTERS])
         ),
     ).tag(config=True)
 
     @observe("shortcuts")
     def _shortcuts_changed(self, change):
         if self.pt_app:
             self.pt_app.key_bindings = self._merge_shortcuts(user_shortcuts=change.new)
 
     def _merge_shortcuts(self, user_shortcuts):
         # rebuild the bindings list from scratch
         key_bindings = create_ipython_shortcuts(self)
 
         # for now we only allow adding shortcuts for commands which are already
         # registered; this is a security precaution.
         known_commands = {
             create_identifier(binding.handler): binding.handler
             for binding in key_bindings.bindings
         }
         shortcuts_to_skip = []
         shortcuts_to_add = []
 
         for shortcut in user_shortcuts:
             command_id = shortcut["command"]
             if command_id not in known_commands:
                 allowed_commands = "\n - ".join(known_commands)
                 raise ValueError(
                     f"{command_id} is not a known shortcut command."
                     f" Allowed commands are: \n - {allowed_commands}"
                 )
             old_keys = shortcut.get("match_keys", None)
             old_filter = (
                 filter_from_string(shortcut["match_filter"])
                 if "match_filter" in shortcut
                 else None
             )
             matching = [
                 binding
                 for binding in key_bindings.bindings
                 if (
                     (old_filter is None or binding.filter == old_filter)
                     and (old_keys is None or [k for k in binding.keys] == old_keys)
                     and create_identifier(binding.handler) == command_id
                 )
             ]
 
             new_keys = shortcut.get("new_keys", None)
             new_filter = shortcut.get("new_filter", None)
 
             command = known_commands[command_id]
 
             creating_new = shortcut.get("create", False)
             modifying_existing = not creating_new and (
                 new_keys is not None or new_filter
             )
 
             if creating_new and new_keys == []:
                 raise ValueError("Cannot add a shortcut without keys")
 
             if modifying_existing:
                 specification = {
                     key: shortcut[key]
                     for key in ["command", "filter"]
                     if key in shortcut
                 }
                 if len(matching) == 0:
                     raise ValueError(f"No shortcuts matching {specification} found")
                 elif len(matching) > 1:
                     raise ValueError(
                         f"Multiple shortcuts matching {specification} found,"
                         f" please add keys/filter to select one of: {matching}"
                     )
 
                 matched = matching[0]
                 old_filter = matched.filter
                 old_keys = list(matched.keys)
                 shortcuts_to_skip.append(
                     RuntimeBinding(
                         command,
                         keys=old_keys,
                         filter=old_filter,
                     )
                 )
 
             if new_keys != []:
                 shortcuts_to_add.append(
                     RuntimeBinding(
                         command,
                         keys=new_keys or old_keys,
                         filter=filter_from_string(new_filter)
                         if new_filter is not None
                         else (
                             old_filter
                             if old_filter is not None
                             else filter_from_string("always")
                         ),
                     )
                 )
 
         # rebuild the bindings list from scratch
         key_bindings = create_ipython_shortcuts(self, skip=shortcuts_to_skip)
         for binding in shortcuts_to_add:
             add_binding(key_bindings, binding)
 
         return key_bindings
 
     prompt_includes_vi_mode = Bool(True,
         help="Display the current vi mode (when using vi editing mode)."
     ).tag(config=True)
 
     @observe('term_title')
     def init_term_title(self, change=None):
         # Enable or disable the terminal title.
         if self.term_title and _is_tty:
             toggle_set_term_title(True)
             set_term_title(self.term_title_format.format(cwd=abbrev_cwd()))
         else:
             toggle_set_term_title(False)
 
     def restore_term_title(self):
         if self.term_title and _is_tty:
             restore_term_title()
 
     def init_display_formatter(self):
         super(TerminalInteractiveShell, self).init_display_formatter()
         # terminal only supports plain text
         self.display_formatter.active_types = ["text/plain"]
 
     def init_prompt_toolkit_cli(self):
         if self.simple_prompt:
             # Fall back to plain non-interactive output for tests.
             # This is very limited.
             def prompt():
                 prompt_text = "".join(x[1] for x in self.prompts.in_prompt_tokens())
                 lines = [input(prompt_text)]
                 prompt_continuation = "".join(x[1] for x in self.prompts.continuation_prompt_tokens())
                 while self.check_complete('\n'.join(lines))[0] == 'incomplete':
                     lines.append( input(prompt_continuation) )
                 return '\n'.join(lines)
             self.prompt_for_code = prompt
             return
 
         # Set up keyboard shortcuts
         key_bindings = self._merge_shortcuts(user_shortcuts=self.shortcuts)
 
         # Pre-populate history from IPython's history database
         history = PtkHistoryAdapter(self)
 
         self._style = self._make_style_from_name_or_cls(self.highlighting_style)
         self.style = DynamicStyle(lambda: self._style)
 
         editing_mode = getattr(EditingMode, self.editing_mode.upper())
 
         self.pt_loop = asyncio.new_event_loop()
         self.pt_app = PromptSession(
             auto_suggest=self.auto_suggest,
             editing_mode=editing_mode,
             key_bindings=key_bindings,
             history=history,
             completer=IPythonPTCompleter(shell=self),
             enable_history_search=self.enable_history_search,
             style=self.style,
             include_default_pygments_style=False,
             mouse_support=self.mouse_support,
             enable_open_in_editor=self.extra_open_editor_shortcuts,
             color_depth=self.color_depth,
             tempfile_suffix=".py",
             **self._extra_prompt_options(),
         )
         if isinstance(self.auto_suggest, NavigableAutoSuggestFromHistory):
             self.auto_suggest.connect(self.pt_app)
 
     def _make_style_from_name_or_cls(self, name_or_cls):
         """
         Small wrapper that make an IPython compatible style from a style name
 
         We need that to add style for prompt ... etc.
         """
         style_overrides = {}
         if name_or_cls == 'legacy':
             legacy = self.colors.lower()
             if legacy == 'linux':
                 style_cls = get_style_by_name('monokai')
                 style_overrides = _style_overrides_linux
             elif legacy == 'lightbg':
                 style_overrides = _style_overrides_light_bg
                 style_cls = get_style_by_name('pastie')
             elif legacy == 'neutral':
                 # The default theme needs to be visible on both a dark background
                 # and a light background, because we can't tell what the terminal
                 # looks like. These tweaks to the default theme help with that.
                 style_cls = get_style_by_name('default')
                 style_overrides.update({
                     Token.Number: '#ansigreen',
                     Token.Operator: 'noinherit',
                     Token.String: '#ansiyellow',
                     Token.Name.Function: '#ansiblue',
                     Token.Name.Class: 'bold #ansiblue',
                     Token.Name.Namespace: 'bold #ansiblue',
                     Token.Name.Variable.Magic: '#ansiblue',
                     Token.Prompt: '#ansigreen',
                     Token.PromptNum: '#ansibrightgreen bold',
                     Token.OutPrompt: '#ansired',
                     Token.OutPromptNum: '#ansibrightred bold',
                 })
 
                 # Hack: Due to limited color support on the Windows console
                 # the prompt colors will be wrong without this
                 if os.name == 'nt':
                     style_overrides.update({
                         Token.Prompt: '#ansidarkgreen',
                         Token.PromptNum: '#ansigreen bold',
                         Token.OutPrompt: '#ansidarkred',
                         Token.OutPromptNum: '#ansired bold',
                     })
             elif legacy =='nocolor':
                 style_cls=_NoStyle
                 style_overrides = {}
             else :
                 raise ValueError('Got unknown colors: ', legacy)
         else :
             if isinstance(name_or_cls, str):
                 style_cls = get_style_by_name(name_or_cls)
             else:
                 style_cls = name_or_cls
             style_overrides = {
                 Token.Prompt: '#ansigreen',
                 Token.PromptNum: '#ansibrightgreen bold',
                 Token.OutPrompt: '#ansired',
                 Token.OutPromptNum: '#ansibrightred bold',
             }
         style_overrides.update(self.highlighting_style_overrides)
         style = merge_styles([
             style_from_pygments_cls(style_cls),
             style_from_pygments_dict(style_overrides),
         ])
 
         return style
 
     @property
     def pt_complete_style(self):
         return {
             'multicolumn': CompleteStyle.MULTI_COLUMN,
             'column': CompleteStyle.COLUMN,
             'readlinelike': CompleteStyle.READLINE_LIKE,
         }[self.display_completions]
 
     @property
     def color_depth(self):
         return (ColorDepth.TRUE_COLOR if self.true_color else None)
 
     def _extra_prompt_options(self):
         """
         Return the current layout option for the current Terminal InteractiveShell
         """
         def get_message():
             return PygmentsTokens(self.prompts.in_prompt_tokens())
 
         if self.editing_mode == 'emacs':
             # with emacs mode the prompt is (usually) static, so we call only
             # the function once. With VI mode it can toggle between [ins] and
             # [nor] so we can't precompute.
             # here I'm going to favor the default keybinding which almost
             # everybody uses to decrease CPU usage.
             # if we have issues with users with custom Prompts we can see how to
             # work around this.
             get_message = get_message()
 
         options = {
             "complete_in_thread": False,
             "lexer": IPythonPTLexer(),
             "reserve_space_for_menu": self.space_for_menu,
             "message": get_message,
             "prompt_continuation": (
                 lambda width, lineno, is_soft_wrap: PygmentsTokens(
                     self.prompts.continuation_prompt_tokens(width)
                 )
             ),
             "multiline": True,
             "complete_style": self.pt_complete_style,
             "input_processors": [
                 # Highlight matching brackets, but only when this setting is
                 # enabled, and only when the DEFAULT_BUFFER has the focus.
                 ConditionalProcessor(
                     processor=HighlightMatchingBracketProcessor(chars="[](){}"),
                     filter=HasFocus(DEFAULT_BUFFER)
                     & ~IsDone()
                     & Condition(lambda: self.highlight_matching_brackets),
                 ),
                 # Show auto-suggestion in lines other than the last line.
                 ConditionalProcessor(
                     processor=AppendAutoSuggestionInAnyLine(),
                     filter=HasFocus(DEFAULT_BUFFER)
                     & ~IsDone()
                     & Condition(
                         lambda: isinstance(
                             self.auto_suggest, NavigableAutoSuggestFromHistory
                         )
                     ),
                 ),
             ],
         }
         if not PTK3:
             options['inputhook'] = self.inputhook
 
         return options
 
     def prompt_for_code(self):
         if self.rl_next_input:
             default = self.rl_next_input
             self.rl_next_input = None
         else:
             default = ''
 
         # In order to make sure that asyncio code written in the
         # interactive shell doesn't interfere with the prompt, we run the
         # prompt in a different event loop.
         # If we don't do this, people could spawn coroutine with a
         # while/true inside which will freeze the prompt.
 
         policy = asyncio.get_event_loop_policy()
         old_loop = get_asyncio_loop()
 
         # FIXME: prompt_toolkit is using the deprecated `asyncio.get_event_loop`
         # to get the current event loop.
         # This will probably be replaced by an attribute or input argument,
         # at which point we can stop calling the soon-to-be-deprecated `set_event_loop` here.
         if old_loop is not self.pt_loop:
             policy.set_event_loop(self.pt_loop)
         try:
             with patch_stdout(raw=True):
                 text = self.pt_app.prompt(
                     default=default,
                     **self._extra_prompt_options())
         finally:
             # Restore the original event loop.
             if old_loop is not None and old_loop is not self.pt_loop:
                 policy.set_event_loop(old_loop)
 
         return text
 
     def enable_win_unicode_console(self):
         # Since IPython 7.10 doesn't support python < 3.6 and PEP 528, Python uses the unicode APIs for the Windows
         # console by default, so WUC shouldn't be needed.
         warn("`enable_win_unicode_console` is deprecated since IPython 7.10, does not do anything and will be removed in the future",
              DeprecationWarning,
              stacklevel=2)
 
     def init_io(self):
         if sys.platform not in {'win32', 'cli'}:
             return
 
         import colorama
         colorama.init()
 
     def init_magics(self):
         super(TerminalInteractiveShell, self).init_magics()
         self.register_magics(TerminalMagics)
 
     def init_alias(self):
         # The parent class defines aliases that can be safely used with any
         # frontend.
         super(TerminalInteractiveShell, self).init_alias()
 
         # Now define aliases that only make sense on the terminal, because they
         # need direct access to the console in a way that we can't emulate in
         # GUI or web frontend
         if os.name == 'posix':
             for cmd in ('clear', 'more', 'less', 'man'):
                 self.alias_manager.soft_define_alias(cmd, cmd)
 
 
     def __init__(self, *args, **kwargs) -> None:
         super(TerminalInteractiveShell, self).__init__(*args, **kwargs)
         self._set_autosuggestions(self.autosuggestions_provider)
         self.init_prompt_toolkit_cli()
         self.init_term_title()
         self.keep_running = True
         self._set_formatter(self.autoformatter)
 
 
     def ask_exit(self):
         self.keep_running = False
 
     rl_next_input = None
 
     def interact(self):
         self.keep_running = True
         while self.keep_running:
             print(self.separate_in, end='')
 
             try:
                 code = self.prompt_for_code()
             except EOFError:
                 if (not self.confirm_exit) \
                         or self.ask_yes_no('Do you really want to exit ([y]/n)?','y','n'):
                     self.ask_exit()
 
             else:
                 if code:
                     self.run_cell(code, store_history=True)
 
     def mainloop(self):
         # An extra layer of protection in case someone mashing Ctrl-C breaks
         # out of our internal code.
         while True:
             try:
                 self.interact()
                 break
             except KeyboardInterrupt as e:
                 print("\n%s escaped interact()\n" % type(e).__name__)
             finally:
                 # An interrupt during the eventloop will mess up the
                 # internal state of the prompt_toolkit library.
                 # Stopping the eventloop fixes this, see
                 # https://github.com/ipython/ipython/pull/9867
                 if hasattr(self, '_eventloop'):
                     self._eventloop.stop()
 
                 self.restore_term_title()
 
         # try to call some at-exit operation optimistically as some things can't
         # be done during interpreter shutdown. this is technically inaccurate as
         # this make mainlool not re-callable, but that should be a rare if not
         # in existent use case.
 
         self._atexit_once()
 
 
     _inputhook = None
     def inputhook(self, context):
         if self._inputhook is not None:
             self._inputhook(context)
 
     active_eventloop = None
     def enable_gui(self, gui=None):
+        if self._inputhook is not None and gui is not None:
+            warn(
+                f"Shell was already running a gui event loop for {self.active_eventloop}; switching to {gui}."
+            )
         if gui and (gui not in {"inline", "webagg"}):
+            # This hook runs with each cycle of the `prompt_toolkit`'s event loop.
             self.active_eventloop, self._inputhook = get_inputhook_name_and_func(gui)
         else:
             self.active_eventloop = self._inputhook = None
 
         # For prompt_toolkit 3.0. We have to create an asyncio event loop with
         # this inputhook.
         if PTK3:
             import asyncio
             from prompt_toolkit.eventloop import new_eventloop_with_inputhook
 
             if gui == 'asyncio':
                 # When we integrate the asyncio event loop, run the UI in the
                 # same event loop as the rest of the code. don't use an actual
                 # input hook. (Asyncio is not made for nesting event loops.)
                 self.pt_loop = get_asyncio_loop()
 
             elif self._inputhook:
                 # If an inputhook was set, create a new asyncio event loop with
                 # this inputhook for the prompt.
                 self.pt_loop = new_eventloop_with_inputhook(self._inputhook)
             else:
                 # When there's no inputhook, run the prompt in a separate
                 # asyncio event loop.
                 self.pt_loop = asyncio.new_event_loop()
 
     # Run !system commands directly, not through pipes, so terminal programs
     # work correctly.
     system = InteractiveShell.system_raw
 
     def auto_rewrite_input(self, cmd):
         """Overridden from the parent class to use fancy rewriting prompt"""
         if not self.show_rewritten_input:
             return
 
         tokens = self.prompts.rewrite_prompt_tokens()
         if self.pt_app:
             print_formatted_text(PygmentsTokens(tokens), end='',
                                  style=self.pt_app.app.style)
             print(cmd)
         else:
             prompt = ''.join(s for t, s in tokens)
             print(prompt, cmd, sep='')
 
     _prompts_before = None
     def switch_doctest_mode(self, mode):
         """Switch prompts to classic for %doctest_mode"""
         if mode:
             self._prompts_before = self.prompts
             self.prompts = ClassicPrompts(self)
         elif self._prompts_before:
             self.prompts = self._prompts_before
             self._prompts_before = None
 #        self._update_layout()
 
 
 InteractiveShellABC.register(TerminalInteractiveShell)
 
 if __name__ == '__main__':
     TerminalInteractiveShell.instance().interact()

IPython/terminal/pt_inputhooks/__init__.py

@@ -1,62 +1,132 b''
 import importlib
 import os
 
 aliases = {
     'qt4': 'qt',
     'gtk2': 'gtk',
 }
 
 backends = [
     "qt",
-    "qt4",
     "qt5",
     "qt6",
     "gtk",
     "gtk2",
     "gtk3",
     "gtk4",
     "tk",
     "wx",
     "pyglet",
     "glut",
     "osx",
     "asyncio",
 ]
 
 registered = {}
 
 def register(name, inputhook):
     """Register the function *inputhook* as an event loop integration."""
     registered[name] = inputhook
 
 
 class UnknownBackend(KeyError):
     def __init__(self, name):
         self.name = name
 
     def __str__(self):
         return ("No event loop integration for {!r}. "
                 "Supported event loops are: {}").format(self.name,
                                     ', '.join(backends + sorted(registered)))
 
 
+def set_qt_api(gui):
+    """Sets the `QT_API` environment variable if it isn't already set."""
+
+    qt_api = os.environ.get("QT_API", None)
+
+    from IPython.external.qt_loaders import (
+        QT_API_PYQT,
+        QT_API_PYQT5,
+        QT_API_PYQT6,
+        QT_API_PYSIDE,
+        QT_API_PYSIDE2,
+        QT_API_PYSIDE6,
+        QT_API_PYQTv1,
+        loaded_api,
+    )
+
+    loaded = loaded_api()
+
+    qt_env2gui = {
+        QT_API_PYSIDE: "qt4",
+        QT_API_PYQTv1: "qt4",
+        QT_API_PYQT: "qt4",
+        QT_API_PYSIDE2: "qt5",
+        QT_API_PYQT5: "qt5",
+        QT_API_PYSIDE6: "qt6",
+        QT_API_PYQT6: "qt6",
+    }
+    if loaded is not None and gui != "qt":
+        if qt_env2gui[loaded] != gui:
+            print(
+                f"Cannot switch Qt versions for this session; must use {qt_env2gui[loaded]}."
+            )
+            return
+
+    if qt_api is not None and gui != "qt":
+        if qt_env2gui[qt_api] != gui:
+            print(
+                f'Request for "{gui}" will be ignored because `QT_API` '
+                f'environment variable is set to "{qt_api}"'
+            )
+    else:
+        if gui == "qt5":
+            try:
+                import PyQt5  # noqa
+
+                os.environ["QT_API"] = "pyqt5"
+            except ImportError:
+                try:
+                    import PySide2  # noqa
+
+                    os.environ["QT_API"] = "pyside2"
+                except ImportError:
+                    os.environ["QT_API"] = "pyqt5"
+        elif gui == "qt6":
+            try:
+                import PyQt6  # noqa
+
+                os.environ["QT_API"] = "pyqt6"
+            except ImportError:
+                try:
+                    import PySide6  # noqa
+
+                    os.environ["QT_API"] = "pyside6"
+                except ImportError:
+                    os.environ["QT_API"] = "pyqt6"
+        elif gui == "qt":
+            # Don't set QT_API; let IPython logic choose the version.
+            if "QT_API" in os.environ.keys():
+                del os.environ["QT_API"]
+        else:
+            print(f'Unrecognized Qt version: {gui}. Should be "qt5", "qt6", or "qt".')
+            return
+
+
 def get_inputhook_name_and_func(gui):
     if gui in registered:
         return gui, registered[gui]
 
     if gui not in backends:
         raise UnknownBackend(gui)
 
     if gui in aliases:
         return get_inputhook_name_and_func(aliases[gui])
 
     gui_mod = gui
-    if gui == "qt5":
-        os.environ["QT_API"] = "pyqt5"
-        gui_mod = "qt"
-    elif gui == "qt6":
-        os.environ["QT_API"] = "pyqt6"
+    if gui.startswith("qt"):
+        set_qt_api(gui)
         gui_mod = "qt"
 
-    mod = importlib.import_module('IPython.terminal.pt_inputhooks.'+gui_mod)
+    mod = importlib.import_module("IPython.terminal.pt_inputhooks." + gui_mod)
     return gui, mod.inputhook

IPython/terminal/pt_inputhooks/qt.py

@@ -1,85 +1,86 b''
 import sys
 import os
 from IPython.external.qt_for_kernel import QtCore, QtGui, enum_helper
 from IPython import get_ipython
 
 # If we create a QApplication, keep a reference to it so that it doesn't get
 # garbage collected.
 _appref = None
 _already_warned = False
 
 
 def _exec(obj):
     # exec on PyQt6, exec_ elsewhere.
     obj.exec() if hasattr(obj, "exec") else obj.exec_()
 
 
 def _reclaim_excepthook():
     shell = get_ipython()
     if shell is not None:
         sys.excepthook = shell.excepthook
 
 
 def inputhook(context):
     global _appref
     app = QtCore.QCoreApplication.instance()
     if not app:
         if sys.platform == 'linux':
             if not os.environ.get('DISPLAY') \
                     and not os.environ.get('WAYLAND_DISPLAY'):
                 import warnings
                 global _already_warned
                 if not _already_warned:
                     _already_warned = True
                     warnings.warn(
                         'The DISPLAY or WAYLAND_DISPLAY environment variable is '
                         'not set or empty and Qt5 requires this environment '
                         'variable. Deactivate Qt5 code.'
                     )
                 return
         try:
             QtCore.QApplication.setAttribute(QtCore.Qt.AA_EnableHighDpiScaling)
         except AttributeError:  # Only for Qt>=5.6, <6.
             pass
         try:
             QtCore.QApplication.setHighDpiScaleFactorRoundingPolicy(
                 QtCore.Qt.HighDpiScaleFactorRoundingPolicy.PassThrough
             )
         except AttributeError:  # Only for Qt>=5.14.
             pass
         _appref = app = QtGui.QApplication([" "])
 
         # "reclaim" IPython sys.excepthook after event loop starts
         # without this, it defaults back to BaseIPythonApplication.excepthook
         # and exceptions in the Qt event loop are rendered without traceback
         # formatting and look like "bug in IPython".
         QtCore.QTimer.singleShot(0, _reclaim_excepthook)
 
     event_loop = QtCore.QEventLoop(app)
 
     if sys.platform == 'win32':
         # The QSocketNotifier method doesn't appear to work on Windows.
         # Use polling instead.
         timer = QtCore.QTimer()
         timer.timeout.connect(event_loop.quit)
         while not context.input_is_ready():
+            # NOTE: run the event loop, and after 50 ms, call `quit` to exit it.
             timer.start(50)  # 50 ms
             _exec(event_loop)
             timer.stop()
     else:
         # On POSIX platforms, we can use a file descriptor to quit the event
         # loop when there is input ready to read.
         notifier = QtCore.QSocketNotifier(
             context.fileno(), enum_helper("QtCore.QSocketNotifier.Type").Read
         )
         try:
             # connect the callback we care about before we turn it on
             # lambda is necessary as PyQT inspect the function signature to know
             # what arguments to pass to. See https://github.com/ipython/ipython/pull/12355
             notifier.activated.connect(lambda: event_loop.exit())
             notifier.setEnabled(True)
             # only start the event loop we are not already flipped
             if not context.input_is_ready():
                 _exec(event_loop)
         finally:
             notifier.setEnabled(False)

docs/source/config/eventloops.rst

@@ -1,108 +1,108 b''
 ================================
 Integrating with GUI event loops
 ================================
 
 When the user types ``%gui qt``, IPython integrates itself with the Qt event
 loop, so you can use both a GUI and an interactive prompt together. IPython
 supports a number of common GUI toolkits, but from IPython 3.0, it is possible
 to integrate other event loops without modifying IPython itself.
 
-Supported event loops include ``qt4``, ``qt5``, ``gtk2``, ``gtk3``, ``gtk4``,
+Supported event loops include ``qt5``, ``qt6``, ``gtk2``, ``gtk3``, ``gtk4``,
 ``wx``, ``osx`` and ``tk``. Make sure the event loop you specify matches the
 GUI toolkit used by your own code.
 
 To make IPython GUI event loop integration occur automatically at every
 startup, set the ``c.InteractiveShellApp.gui`` configuration key in your
 IPython profile (see :ref:`setting_config`).
 
 If the event loop you use is supported by IPython, turning on event loop
 integration follows the steps just described whether you use Terminal IPython
 or an IPython kernel.
 
 However, the way Terminal IPython handles event loops is very different from
 the way IPython kernel does, so if you need to integrate with a new kind of
 event loop, different steps are needed to integrate with each.
 
 Integrating with a new event loop in the terminal
 -------------------------------------------------
 
 .. versionchanged:: 5.0
 
    There is a new API for event loop integration using prompt_toolkit.
 
 In the terminal, IPython uses prompt_toolkit to prompt the user for input.
 prompt_toolkit provides hooks to integrate with an external event loop.
 
 To integrate an event loop, define a function which runs the GUI event loop
 until there is input waiting for prompt_toolkit to process. There are two ways
 to detect this condition::
 
     # Polling for input.
     def inputhook(context):
         while not context.input_is_ready():
             # Replace this with the appropriate call for the event loop:
             iterate_loop_once()
 
     # Using a file descriptor to notify the event loop to stop.
     def inputhook2(context):
         fd = context.fileno()
         # Replace the functions below with those for the event loop.
         add_file_reader(fd, callback=stop_the_loop)
         run_the_loop()
 
 Once you have defined this function, register it with IPython:
 
 .. currentmodule:: IPython.terminal.pt_inputhooks
 
 .. function:: register(name, inputhook)
 
    Register the function *inputhook* as the event loop integration for the
    GUI *name*. If ``name='foo'``, then the user can enable this integration
    by running ``%gui foo``.
 
 
 Integrating with a new event loop in the kernel
 -----------------------------------------------
 
 The kernel runs its own event loop, so it's simpler to integrate with others.
 IPython allows the other event loop to take control, but it must call
 :meth:`IPython.kernel.zmq.kernelbase.Kernel.do_one_iteration` periodically.
 
 To integrate with this, write a function that takes a single argument,
 the IPython kernel instance, arranges for your event loop to call
 ``kernel.do_one_iteration()`` at least every ``kernel._poll_interval`` seconds,
 and starts the event loop.
 
 Decorate this function with :func:`IPython.kernel.zmq.eventloops.register_integration`,
 passing in the names you wish to register it for. Here is a slightly simplified
 version of the Tkinter integration already included in IPython::
 
     @register_integration('tk')
     def loop_tk(kernel):
         """Start a kernel with the Tk event loop."""
         from tkinter import Tk
 
         # Tk uses milliseconds
         poll_interval = int(1000*kernel._poll_interval)
         # For Tkinter, we create a Tk object and call its withdraw method.
         class Timer(object):
             def __init__(self, func):
                 self.app = Tk()
                 self.app.withdraw()
                 self.func = func
 
             def on_timer(self):
                 self.func()
                 self.app.after(poll_interval, self.on_timer)
 
             def start(self):
                 self.on_timer()  # Call it once to get things going.
                 self.app.mainloop()
 
         kernel.timer = Timer(kernel.do_one_iteration)
         kernel.timer.start()
 
 Some event loops can go one better, and integrate checking for messages on the
 kernel's ZMQ sockets, making the kernel more responsive than plain polling. How
 to do this is outside the scope of this document; if you are interested, look at
 the integration with Qt in :mod:`IPython.kernel.zmq.eventloops`.

docs/source/interactive/reference.rst

@@ -1,1044 +1,1037 b''
 =================
 IPython reference
 =================
 
 .. _command_line_options:
 
 Command-line usage
 ==================
 
 You start IPython with the command::
 
     $ ipython [options] files
 
 If invoked with no options, it executes the file and exits, passing the
 remaining arguments to the script, just as if you had specified the same
 command with python. You may need to specify `--` before args to be passed
 to the script, to prevent IPython from attempting to parse them.
 If you add the ``-i`` flag, it drops you into the interpreter while still
 acknowledging any options you may have set in your ``ipython_config.py``. This
 behavior is different from standard Python, which when called as python ``-i``
 will only execute one file and ignore your configuration setup.
 
 Please note that some of the configuration options are not available at the
 command line, simply because they are not practical here. Look into your
 configuration files for details on those. There are separate configuration files
 for each profile, and the files look like :file:`ipython_config.py` or
 :file:`ipython_config_{frontendname}.py`.  Profile directories look like
 :file:`profile_{profilename}` and are typically installed in the
 :envvar:`IPYTHONDIR` directory, which defaults to :file:`$HOME/.ipython`. For
 Windows users, :envvar:`HOME` resolves to :file:`C:\\Users\\{YourUserName}` in
 most instances.
 
 Command-line Options
 --------------------
 
 To see the options IPython accepts, use ``ipython --help`` (and you probably
 should run the output through a pager such as ``ipython --help | less`` for
 more convenient reading).  This shows all the options that have a single-word
 alias to control them, but IPython lets you configure all of its objects from
 the command-line by passing the full class name and a corresponding value; type
 ``ipython --help-all`` to see this full list.  For example::
 
     $ ipython --help-all
     <...snip...>
     --matplotlib=<CaselessStrEnum> (InteractiveShellApp.matplotlib)
         Default: None
-        Choices: ['auto', 'gtk', 'gtk3', 'gtk4', 'inline', 'nbagg', 'notebook', 'osx', 'qt', 'qt4', 'qt5', 'tk', 'wx']
+        Choices: ['auto', 'gtk', 'gtk3', 'gtk4', 'inline', 'nbagg', 'notebook', 'osx', 'qt', 'qt5', 'qt6', 'tk', 'wx']
         Configure matplotlib for interactive use with the default matplotlib
         backend.
     <...snip...>
 
 
 Indicate that the following::
 
    $ ipython --matplotlib qt
 
 
 is equivalent to::
 
    $ ipython --InteractiveShellApp.matplotlib='qt'
 
 Note that in the second form, you *must* use the equal sign, as the expression
 is evaluated as an actual Python assignment.  While in the above example the
 short form is more convenient, only the most common options have a short form,
 while any configurable variable in IPython can be set at the command-line by
 using the long form.  This long form is the same syntax used in the
 configuration files, if you want to set these options permanently.
 
 
 Interactive use
 ===============
 
 IPython is meant to work as a drop-in replacement for the standard interactive
 interpreter. As such, any code which is valid python should execute normally
 under IPython (cases where this is not true should be reported as bugs). It
 does, however, offer many features which are not available at a standard python
 prompt. What follows is a list of these.
 
 
 Caution for Windows users
 -------------------------
 
 Windows, unfortunately, uses the ``\`` character as a path separator. This is a
 terrible choice, because ``\`` also represents the escape character in most
 modern programming languages, including Python. For this reason, using '/'
 character is recommended if you have problems with ``\``.  However, in Windows
 commands '/' flags options, so you can not use it for the root directory. This
 means that paths beginning at the root must be typed in a contrived manner
 like: ``%copy \opt/foo/bar.txt \tmp``
 
 .. _magic:
 
 Magic command system
 --------------------
 
 IPython will treat any line whose first character is a % as a special
 call to a 'magic' function. These allow you to control the behavior of
 IPython itself, plus a lot of system-type features. They are all
 prefixed with a % character, but parameters are given without
 parentheses or quotes.
 
 Lines that begin with ``%%`` signal a *cell magic*: they take as arguments not
 only the rest of the current line, but all lines below them as well, in the
 current execution block.  Cell magics can in fact make arbitrary modifications
 to the input they receive, which need not even be valid Python code at all.
 They receive the whole block as a single string.
 
 As a line magic example, the :magic:`cd` magic works just like the OS command of
 the same name::
 
       In [8]: %cd
       /home/fperez
 
 The following uses the builtin :magic:`timeit` in cell mode::
 
   In [10]: %%timeit x = range(10000)
       ...: min(x)
       ...: max(x)
       ...:
   1000 loops, best of 3: 438 us per loop
 
 In this case, ``x = range(10000)`` is called as the line argument, and the
 block with ``min(x)`` and ``max(x)`` is called as the cell body.  The
 :magic:`timeit` magic receives both.
 
 If you have 'automagic' enabled (as it is by default), you don't need to type in
 the single ``%`` explicitly for line magics; IPython will scan its internal
 list of magic functions and call one if it exists. With automagic on you can
 then just type ``cd mydir`` to go to directory 'mydir'::
 
       In [9]: cd mydir
       /home/fperez/mydir
 
 Cell magics *always* require an explicit ``%%`` prefix, automagic
 calling only works for line magics.
 
 The automagic system has the lowest possible precedence in name searches, so
 you can freely use variables with the same names as magic commands. If a magic
 command is 'shadowed' by a variable, you will need the explicit ``%`` prefix to
 use it:
 
 .. sourcecode:: ipython
 
     In [1]: cd ipython     # %cd is called by automagic
     /home/fperez/ipython
 
     In [2]: cd=1 	   # now cd is just a variable
 
     In [3]: cd .. 	   # and doesn't work as a function anymore
     File "<ipython-input-3-9fedb3aff56c>", line 1
       cd ..
           ^
     SyntaxError: invalid syntax
 
 
     In [4]: %cd .. 	   # but %cd always works
     /home/fperez
 
     In [5]: del cd     # if you remove the cd variable, automagic works again
 
     In [6]: cd ipython
 
     /home/fperez/ipython
 
 Line magics, if they return a value, can be assigned to a variable using the
 syntax ``l = %sx ls`` (which in this particular case returns the result of `ls`
 as a python list). See :ref:`below <manual_capture>` for more information.
 
 Type ``%magic`` for more information, including a list of all available magic
 functions at any time and their docstrings. You can also type
 ``%magic_function_name?`` (see :ref:`below <dynamic_object_info>` for
 information on the '?' system) to get information about any particular magic
 function you are interested in.
 
 The API documentation for the :mod:`IPython.core.magic` module contains the full
 docstrings of all currently available magic commands.
 
 .. seealso::
 
    :doc:`magics`
      A list of the line and cell magics available in IPython by default
 
    :ref:`defining_magics`
      How to define and register additional magic functions
 
 
 Access to the standard Python help
 ----------------------------------
 
 Simply type ``help()`` to access Python's standard help system. You can
 also type ``help(object)`` for information about a given object, or
 ``help('keyword')`` for information on a keyword. You may need to configure your
 PYTHONDOCS environment variable for this feature to work correctly.
 
 .. _dynamic_object_info:
 
 Dynamic object information
 --------------------------
 
 Typing ``?word`` or ``word?`` prints detailed information about an object. If
 certain strings in the object are too long (e.g. function signatures) they get
 snipped in the center for brevity. This system gives access variable types and
 values, docstrings, function prototypes and other useful information.
 
 If the information will not fit in the terminal, it is displayed in a pager
 (``less`` if available, otherwise a basic internal pager).
 
 Typing ``??word`` or ``word??`` gives access to the full information, including
 the source code where possible. Long strings are not snipped.
 
 The following magic functions are particularly useful for gathering
 information about your working environment:
 
     * :magic:`pdoc` **<object>**: Print (or run through a pager if too long) the
       docstring for an object. If the given object is a class, it will
       print both the class and the constructor docstrings.
     * :magic:`pdef` **<object>**: Print the call signature for any callable
       object. If the object is a class, print the constructor information.
     * :magic:`psource` **<object>**: Print (or run through a pager if too long)
       the source code for an object.
     * :magic:`pfile` **<object>**: Show the entire source file where an object was
       defined via a pager, opening it at the line where the object
       definition begins.
     * :magic:`who`/:magic:`whos`: These functions give information about identifiers
       you have defined interactively (not things you loaded or defined
       in your configuration files). %who just prints a list of
       identifiers and %whos prints a table with some basic details about
       each identifier.
 
 The dynamic object information functions (?/??, ``%pdoc``,
 ``%pfile``, ``%pdef``, ``%psource``) work on object attributes, as well as
 directly on variables. For example, after doing ``import os``, you can use
 ``os.path.abspath??``.
 
 
 Command line completion
 +++++++++++++++++++++++
 
 At any time, hitting TAB will complete any available python commands or
 variable names, and show you a list of the possible completions if
 there's no unambiguous one. It will also complete filenames in the
 current directory if no python names match what you've typed so far.
 
 
 Search command history
 ++++++++++++++++++++++
 
 IPython provides two ways for searching through previous input and thus
 reduce the need for repetitive typing:
 
    1. Start typing, and then use the up and down arrow keys (or :kbd:`Ctrl-p`
       and :kbd:`Ctrl-n`) to search through only the history items that match
       what you've typed so far.
    2. Hit :kbd:`Ctrl-r`: to open a search prompt. Begin typing and the system
       searches your history for lines that contain what you've typed so
       far, completing as much as it can.
 
 IPython will save your input history when it leaves and reload it next
 time you restart it. By default, the history file is named
 :file:`.ipython/profile_{name}/history.sqlite`.
 
 Autoindent
 ++++++++++
 
 Starting with 5.0, IPython uses `prompt_toolkit` in place of ``readline``,
 it thus can recognize lines ending in ':' and indent the next line,
 while also un-indenting automatically after 'raise' or 'return',
 and support real multi-line editing as well as syntactic coloration
 during edition.
 
 This feature does not use the ``readline`` library anymore, so it will
 not honor your :file:`~/.inputrc` configuration (or whatever
 file your :envvar:`INPUTRC` environment variable points to).
 
 In particular if you want to change the input mode to ``vi``, you will need to
 set the ``TerminalInteractiveShell.editing_mode`` configuration  option of IPython.
 
 Session logging and restoring
 -----------------------------
 
 You can log all input from a session either by starting IPython with the
 command line switch ``--logfile=foo.py`` (see :ref:`here <command_line_options>`)
 or by activating the logging at any moment with the magic function :magic:`logstart`.
 
 Log files can later be reloaded by running them as scripts and IPython
 will attempt to 'replay' the log by executing all the lines in it, thus
 restoring the state of a previous session. This feature is not quite
 perfect, but can still be useful in many cases.
 
 The log files can also be used as a way to have a permanent record of
 any code you wrote while experimenting. Log files are regular text files
 which you can later open in your favorite text editor to extract code or
 to 'clean them up' before using them to replay a session.
 
 The :magic:`logstart` function for activating logging in mid-session is used as
 follows::
 
     %logstart [log_name [log_mode]]
 
 If no name is given, it defaults to a file named 'ipython_log.py' in your
 current working directory, in 'rotate' mode (see below).
 
 '%logstart name' saves to file 'name' in 'backup' mode. It saves your
 history up to that point and then continues logging.
 
 %logstart takes a second optional parameter: logging mode. This can be
 one of (note that the modes are given unquoted):
 
     * [over:] overwrite existing log_name.
     * [backup:] rename (if exists) to log_name~ and start log_name.
     * [append:] well, that says it.
     * [rotate:] create rotating logs log_name.1~, log_name.2~, etc.
 
 Adding the '-o' flag to '%logstart' magic (as in '%logstart -o [log_name [log_mode]]')
 will also include output from iPython in the log file.
 
 The :magic:`logoff` and :magic:`logon` functions allow you to temporarily stop and
 resume logging to a file which had previously been started with
 %logstart. They will fail (with an explanation) if you try to use them
 before logging has been started.
 
 .. _system_shell_access:
 
 System shell access
 -------------------
 
 Any input line beginning with a ``!`` character is passed verbatim (minus
 the ``!``, of course) to the underlying operating system. For example,
 typing ``!ls`` will run 'ls' in the current directory.
 
 .. _manual_capture:
 
 Manual capture of command output and magic output
 -------------------------------------------------
 
 You can assign the result of a system command to a Python variable with the
 syntax ``myfiles = !ls``. Similarly, the result of a magic (as long as it returns
 a value) can be assigned to a variable.  For example, the syntax ``myfiles = %sx ls``
 is equivalent to the above system command example (the :magic:`sx` magic runs a shell command
 and captures the output).  Each of these gets machine
 readable output from stdout (e.g. without colours), and splits on newlines. To
 explicitly get this sort of output without assigning to a variable, use two
 exclamation marks (``!!ls``) or the :magic:`sx` magic command without an assignment.
 (However, ``!!`` commands cannot be assigned to a variable.)
 
 The captured list in this example has some convenience features. ``myfiles.n`` or ``myfiles.s``
 returns a string delimited by newlines or spaces, respectively. ``myfiles.p``
 produces `path objects <http://pypi.python.org/pypi/path.py>`_ from the list items.
 See :ref:`string_lists` for details.
 
 IPython also allows you to expand the value of python variables when
 making system calls. Wrap variables or expressions in {braces}::
 
     In [1]: pyvar = 'Hello world'
     In [2]: !echo "A python variable: {pyvar}"
     A python variable: Hello world
     In [3]: import math
     In [4]: x = 8
     In [5]: !echo {math.factorial(x)}
     40320
 
 For simple cases, you can alternatively prepend $ to a variable name::
 
     In [6]: !echo $sys.argv
     [/home/fperez/usr/bin/ipython]
     In [7]: !echo "A system variable: $$HOME"  # Use $$ for literal $
     A system variable: /home/fperez
 
 Note that `$$` is used to represent a literal `$`.
 
 System command aliases
 ----------------------
 
 The :magic:`alias` magic function allows you to define magic functions which are in fact
 system shell commands. These aliases can have parameters.
 
 ``%alias alias_name cmd`` defines 'alias_name' as an alias for 'cmd'
 
 Then, typing ``alias_name params`` will execute the system command 'cmd
 params' (from your underlying operating system).
 
 You can also define aliases with parameters using ``%s`` specifiers (one per
 parameter). The following example defines the parts function as an
 alias to the command ``echo first %s second %s`` where each ``%s`` will be
 replaced by a positional parameter to the call to %parts::
 
     In [1]: %alias parts echo first %s second %s
     In [2]: parts A B
     first A second B
     In [3]: parts A
     ERROR: Alias <parts> requires 2 arguments, 1 given.
 
 If called with no parameters, :magic:`alias` prints the table of currently
 defined aliases.
 
 The :magic:`rehashx` magic allows you to load your entire $PATH as
 ipython aliases. See its docstring for further details.
 
 
 .. _dreload:
 
 Recursive reload
 ----------------
 
 The :mod:`IPython.lib.deepreload` module allows you to recursively reload a
 module: changes made to any of its dependencies will be reloaded without
 having to exit. To start using it, do::
 
     from IPython.lib.deepreload import reload as dreload
 
 
 Verbose and colored exception traceback printouts
 -------------------------------------------------
 
 IPython provides the option to see very detailed exception tracebacks,
 which can be especially useful when debugging large programs. You can
 run any Python file with the %run function to benefit from these
 detailed tracebacks. Furthermore, both normal and verbose tracebacks can
 be colored (if your terminal supports it) which makes them much easier
 to parse visually.
 
 See the magic :magic:`xmode` and :magic:`colors` functions for details.
 
 These features are basically a terminal version of Ka-Ping Yee's cgitb
 module, now part of the standard Python library.
 
 
 .. _input_caching:
 
 Input caching system
 --------------------
 
 IPython offers numbered prompts (In/Out) with input and output caching
 (also referred to as 'input history'). All input is saved and can be
 retrieved as variables (besides the usual arrow key recall), in
 addition to the :magic:`rep` magic command that brings a history entry
 up for editing on the next command line.
 
 The following variables always exist:
 
 * ``_i``, ``_ii``, ``_iii``: store previous, next previous and next-next
   previous inputs.
 
 * ``In``, ``_ih`` : a list of all inputs; ``_ih[n]`` is the input from line
   ``n``. If you overwrite In with a variable of your own, you can remake the
   assignment to the internal list with a simple ``In=_ih``.
 
 Additionally, global variables named ``_i<n>`` are dynamically created (``<n>``
 being the prompt counter), so ``_i<n> == _ih[<n>] == In[<n>]``.
 
 For example, what you typed at prompt 14 is available as ``_i14``, ``_ih[14]``
 and ``In[14]``.
 
 This allows you to easily cut and paste multi line interactive prompts
 by printing them out: they print like a clean string, without prompt
 characters. You can also manipulate them like regular variables (they
 are strings), modify or exec them.
 
 You can also re-execute multiple lines of input easily by using the magic
 :magic:`rerun` or :magic:`macro` functions. The macro system also allows you to
 re-execute previous lines which include magic function calls (which require
 special processing). Type %macro? for more details on the macro system.
 
 A history function :magic:`history` allows you to see any part of your input
 history by printing a range of the _i variables.
 
 You can also search ('grep') through your history by typing
 ``%hist -g somestring``. This is handy for searching for URLs, IP addresses,
 etc. You can bring history entries listed by '%hist -g' up for editing
 with the %recall command, or run them immediately with :magic:`rerun`.
 
 .. _output_caching:
 
 Output caching system
 ---------------------
 
 For output that is returned from actions, a system similar to the input
 cache exists but using _ instead of _i. Only actions that produce a
 result (NOT assignments, for example) are cached. If you are familiar
 with Mathematica, IPython's _ variables behave exactly like
 Mathematica's % variables.
 
 The following variables always exist:
 
     * [_] (a single underscore): stores previous output, like Python's
       default interpreter.
     * [__] (two underscores): next previous.
     * [___] (three underscores): next-next previous.
 
 Additionally, global variables named _<n> are dynamically created (<n>
 being the prompt counter), such that the result of output <n> is always
 available as _<n> (don't use the angle brackets, just the number, e.g.
 ``_21``).
 
 These variables are also stored in a global dictionary (not a
 list, since it only has entries for lines which returned a result)
 available under the names _oh and Out (similar to _ih and In). So the
 output from line 12 can be obtained as ``_12``, ``Out[12]`` or ``_oh[12]``. If you
 accidentally overwrite the Out variable you can recover it by typing
 ``Out=_oh`` at the prompt.
 
 This system obviously can potentially put heavy memory demands on your
 system, since it prevents Python's garbage collector from removing any
 previously computed results. You can control how many results are kept
 in memory with the configuration option ``InteractiveShell.cache_size``.
 If you set it to 0, output caching is disabled. You can also use the :magic:`reset`
 and :magic:`xdel` magics to clear large items from memory.
 
 Directory history
 -----------------
 
 Your history of visited directories is kept in the global list _dh, and
 the magic :magic:`cd` command can be used to go to any entry in that list. The
 :magic:`dhist` command allows you to view this history. Do ``cd -<TAB>`` to
 conveniently view the directory history.
 
 
 Automatic parentheses and quotes
 --------------------------------
 
 These features were adapted from Nathan Gray's LazyPython. They are
 meant to allow less typing for common situations.
 
 Callable objects (i.e. functions, methods, etc) can be invoked like this
 (notice the commas between the arguments)::
 
     In [1]: callable_ob arg1, arg2, arg3
     ------> callable_ob(arg1, arg2, arg3)
 
 .. note::
    This feature is disabled by default. To enable it, use the ``%autocall``
    magic command. The commands below with special prefixes will always work,
    however.
 
 You can force automatic parentheses by using '/' as the first character
 of a line. For example::
 
     In [2]: /globals # becomes 'globals()'
 
 Note that the '/' MUST be the first character on the line! This won't work::
 
     In [3]: print /globals # syntax error
 
 In most cases the automatic algorithm should work, so you should rarely
 need to explicitly invoke /. One notable exception is if you are trying
 to call a function with a list of tuples as arguments (the parenthesis
 will confuse IPython)::
 
     In [4]: zip (1,2,3),(4,5,6) # won't work
 
 but this will work::
 
     In [5]: /zip (1,2,3),(4,5,6)
     ------> zip ((1,2,3),(4,5,6))
     Out[5]: [(1, 4), (2, 5), (3, 6)]
 
 IPython tells you that it has altered your command line by displaying
 the new command line preceded by ``--->``.
 
 You can force automatic quoting of a function's arguments by using ``,``
 or ``;`` as the first character of a line. For example::
 
     In [1]: ,my_function /home/me  # becomes my_function("/home/me")
 
 If you use ';' the whole argument is quoted as a single string, while ',' splits
 on whitespace::
 
     In [2]: ,my_function a b c    # becomes my_function("a","b","c")
 
     In [3]: ;my_function a b c    # becomes my_function("a b c")
 
 Note that the ',' or ';' MUST be the first character on the line! This
 won't work::
 
     In [4]: x = ,my_function /home/me # syntax error
 
 IPython as your default Python environment
 ==========================================
 
 Python honors the environment variable :envvar:`PYTHONSTARTUP` and will
 execute at startup the file referenced by this variable. If you put the
 following code at the end of that file, then IPython will be your working
 environment anytime you start Python::
 
     import os, IPython
     os.environ['PYTHONSTARTUP'] = ''  # Prevent running this again
     IPython.start_ipython()
     raise SystemExit
 
 The ``raise SystemExit`` is needed to exit Python when
 it finishes, otherwise you'll be back at the normal Python ``>>>``
 prompt.
 
 This is probably useful to developers who manage multiple Python
 versions and don't want to have correspondingly multiple IPython
 versions. Note that in this mode, there is no way to pass IPython any
 command-line options, as those are trapped first by Python itself.
 
 .. _Embedding:
 
 Embedding IPython
 =================
 
 You can start a regular IPython session with
 
 .. sourcecode:: python
 
     import IPython
     IPython.start_ipython(argv=[])
 
 at any point in your program.  This will load IPython configuration,
 startup files, and everything, just as if it were a normal IPython session.
 For information on setting configuration options when running IPython from
 python, see :ref:`configure_start_ipython`.
 
 It is also possible to embed an IPython shell in a namespace in your Python
 code. This allows you to evaluate dynamically the state of your code, operate
 with your variables, analyze them, etc. For example, if you run the following
 code snippet::
 
   import IPython
 
   a = 42
   IPython.embed()
 
 and within the IPython shell, you reassign `a` to `23` to do further testing of 
 some sort, you can then exit::
 
   >>> IPython.embed()
   Python 3.6.2 (default, Jul 17 2017, 16:44:45) 
   Type 'copyright', 'credits' or 'license' for more information
   IPython 6.2.0.dev -- An enhanced Interactive Python. Type '?' for help.
 
   In [1]: a = 23
 
   In [2]: exit()
 
 Once you exit and print `a`, the value 23 will be shown::
 
 
   In: print(a)
   23
 
 It's important to note that the code run in the embedded IPython shell will 
 *not* change the state of your code and variables, **unless** the shell is 
 contained within the global namespace. In the above example, `a` is changed 
 because this is true.
 
 To further exemplify this, consider the following example::
 
   import IPython
   def do():
       a = 42
       print(a)
       IPython.embed()
       print(a)
 
 Now if call the function and complete the state changes as we did above, the
 value `42` will be printed. Again, this is because it's not in the global
 namespace:: 
 
   do()
 
 Running a file with the above code can lead to the following session::
 
   >>> do()
   42
   Python 3.6.2 (default, Jul 17 2017, 16:44:45) 
   Type 'copyright', 'credits' or 'license' for more information
   IPython 6.2.0.dev -- An enhanced Interactive Python. Type '?' for help.
 
   In [1]: a = 23
 
   In [2]: exit()
   42
 
 .. note::
 
   At present, embedding IPython cannot be done from inside IPython.
   Run the code samples below outside IPython.
 
 This feature allows you to easily have a fully functional python
 environment for doing object introspection anywhere in your code with a
 simple function call. In some cases a simple print statement is enough,
 but if you need to do more detailed analysis of a code fragment this
 feature can be very valuable.
 
 It can also be useful in scientific computing situations where it is
 common to need to do some automatic, computationally intensive part and
 then stop to look at data, plots, etc.
 Opening an IPython instance will give you full access to your data and
 functions, and you can resume program execution once you are done with
 the interactive part (perhaps to stop again later, as many times as
 needed).
 
 The following code snippet is the bare minimum you need to include in
 your Python programs for this to work (detailed examples follow later)::
 
     from IPython import embed
 
     embed() # this call anywhere in your program will start IPython
 
 You can also embed an IPython *kernel*, for use with qtconsole, etc. via
 ``IPython.embed_kernel()``. This should work the same way, but you can
 connect an external frontend (``ipython qtconsole`` or ``ipython console``),
 rather than interacting with it in the terminal.
 
 You can run embedded instances even in code which is itself being run at
 the IPython interactive prompt with '%run <filename>'. Since it's easy
 to get lost as to where you are (in your top-level IPython or in your
 embedded one), it's a good idea in such cases to set the in/out prompts
 to something different for the embedded instances. The code examples
 below illustrate this.
 
 You can also have multiple IPython instances in your program and open
 them separately, for example with different options for data
 presentation. If you close and open the same instance multiple times,
 its prompt counters simply continue from each execution to the next.
 
 Please look at the docstrings in the :mod:`~IPython.frontend.terminal.embed`
 module for more details on the use of this system.
 
 The following sample file illustrating how to use the embedding
 functionality is provided in the examples directory as embed_class_long.py.
 It should be fairly self-explanatory:
 
 .. literalinclude:: ../../../examples/Embedding/embed_class_long.py
     :language: python
 
 Once you understand how the system functions, you can use the following
 code fragments in your programs which are ready for cut and paste:
 
 .. literalinclude:: ../../../examples/Embedding/embed_class_short.py
     :language: python
 
 Using the Python debugger (pdb)
 ===============================
 
 Running entire programs via pdb
 -------------------------------
 
 pdb, the Python debugger, is a powerful interactive debugger which
 allows you to step through code, set breakpoints, watch variables,
 etc.  IPython makes it very easy to start any script under the control
 of pdb, regardless of whether you have wrapped it into a 'main()'
 function or not. For this, simply type ``%run -d myscript`` at an
 IPython prompt. See the :magic:`run` command's documentation for more details, including
 how to control where pdb will stop execution first.
 
 For more information on the use of the pdb debugger, see :ref:`debugger-commands`
 in the Python documentation.
 
 IPython extends the debugger with a few useful additions, like coloring of
 tracebacks. The debugger will adopt the color scheme selected for IPython.
 
 The ``where`` command has also been extended to take as argument the number of
 context line to show. This allows to a many line of context on shallow stack trace:
 
 .. code::
 
     In [5]: def foo(x):
     ...:     1
     ...:     2
     ...:     3
     ...:     return 1/x+foo(x-1)
     ...:     5
     ...:     6
     ...:     7
     ...:
 
     In[6]: foo(1)
     # ...
     ipdb> where 8
     <ipython-input-6-9e45007b2b59>(1)<module>
     ----> 1 foo(1)
 
     <ipython-input-5-7baadc3d1465>(5)foo()
         1 def foo(x):
         2     1
         3     2
         4     3
     ----> 5     return 1/x+foo(x-1)
         6     5
         7     6
         8     7
 
     > <ipython-input-5-7baadc3d1465>(5)foo()
         1 def foo(x):
         2     1
         3     2
         4     3
     ----> 5     return 1/x+foo(x-1)
         6     5
         7     6
         8     7
 
 
 And less context on shallower Stack Trace:
 
 .. code::
 
     ipdb> where 1
     <ipython-input-13-afa180a57233>(1)<module>
     ----> 1 foo(7)
 
     <ipython-input-5-7baadc3d1465>(5)foo()
     ----> 5     return 1/x+foo(x-1)
 
     <ipython-input-5-7baadc3d1465>(5)foo()
     ----> 5     return 1/x+foo(x-1)
 
     <ipython-input-5-7baadc3d1465>(5)foo()
     ----> 5     return 1/x+foo(x-1)
 
     <ipython-input-5-7baadc3d1465>(5)foo()
     ----> 5     return 1/x+foo(x-1)
 
 
 Post-mortem debugging
 ---------------------
 
 Going into a debugger when an exception occurs can be
 extremely useful in order to find the origin of subtle bugs, because pdb
 opens up at the point in your code which triggered the exception, and
 while your program is at this point 'dead', all the data is still
 available and you can walk up and down the stack frame and understand
 the origin of the problem.
 
 You can use the :magic:`debug` magic after an exception has occurred to start
 post-mortem debugging. IPython can also call debugger every time your code
 triggers an uncaught exception. This feature can be toggled with the :magic:`pdb` magic
 command, or you can start IPython with the ``--pdb`` option.
 
 For a post-mortem debugger in your programs outside IPython,
 put the following lines toward the top of your 'main' routine::
 
     import sys
     from IPython.core import ultratb
     sys.excepthook = ultratb.FormattedTB(mode='Verbose',
     color_scheme='Linux', call_pdb=1)
 
 The mode keyword can be either 'Verbose' or 'Plain', giving either very
 detailed or normal tracebacks respectively. The color_scheme keyword can
 be one of 'NoColor', 'Linux' (default) or 'LightBG'. These are the same
 options which can be set in IPython with ``--colors`` and ``--xmode``.
 
 This will give any of your programs detailed, colored tracebacks with
 automatic invocation of pdb.
 
 .. _pasting_with_prompts:
 
 Pasting of code starting with Python or IPython prompts
 =======================================================
 
 IPython is smart enough to filter out input prompts, be they plain Python ones
 (``>>>`` and ``...``) or IPython ones (``In [N]:`` and ``...:``).  You can
 therefore copy and paste from existing interactive sessions without worry.
 
 The following is a 'screenshot' of how things work, copying an example from the
 standard Python tutorial::
 
     In [1]: >>> # Fibonacci series:
 
     In [2]: ... # the sum of two elements defines the next
 
     In [3]: ... a, b = 0, 1
 
     In [4]: >>> while b < 10:
        ...:     ...     print(b)
        ...:     ...     a, b = b, a+b
        ...:
     1
     1
     2
     3
     5
     8
 
 And pasting from IPython sessions works equally well::
 
     In [1]: In [5]: def f(x):
        ...:        ...:     "A simple function"
        ...:        ...:     return x**2
        ...:    ...:
 
     In [2]: f(3)
     Out[2]: 9
 
 .. _gui_support:
 
 GUI event loop support
 ======================
 
 IPython has excellent support for working interactively with Graphical User
-Interface (GUI) toolkits, such as wxPython, PyQt4/PySide, PyGTK and Tk. This is
+Interface (GUI) toolkits, such as wxPython, PyQt/PySide, PyGTK and Tk. This is
 implemented by running the toolkit's event loop while IPython is waiting for
 input.
 
 For users, enabling GUI event loop integration is simple.  You simple use the
 :magic:`gui` magic as follows::
 
     %gui [GUINAME]
 
 With no arguments, ``%gui`` removes all GUI support.  Valid ``GUINAME``
-arguments include ``wx``, ``qt``, ``qt5``, ``gtk``, ``gtk3`` ``gtk4``, and
+arguments include ``wx``, ``qt``, ``qt5``, ``qt6``, ``gtk``, ``gtk3`` ``gtk4``, and
 ``tk``.
 
 Thus, to use wxPython interactively and create a running :class:`wx.App`
 object, do::
 
     %gui wx
 
 You can also start IPython with an event loop set up using the `--gui`
 flag::
 
     $ ipython --gui=qt
 
 For information on IPython's matplotlib_ integration (and the ``matplotlib``
 mode) see :ref:`this section <matplotlib_support>`.
 
 For developers that want to integrate additional event loops with IPython, see
 :doc:`/config/eventloops`.
 
 When running inside IPython with an integrated event loop, a GUI application
 should *not* start its own event loop. This means that applications that are
 meant to be used both
 in IPython and as standalone apps need to have special code to detects how the
 application is being run. We highly recommend using IPython's support for this.
 Since the details vary slightly between toolkits, we point you to the various
 examples in our source directory :file:`examples/IPython Kernel/gui/` that
 demonstrate these capabilities.
 
 PyQt and PySide
 ---------------
 
 .. attempt at explanation of the complete mess that is Qt support
 
 When you use ``--gui=qt`` or ``--matplotlib=qt``, IPython can work with either
-PyQt4 or PySide.  There are three options for configuration here, because
-PyQt4 has two APIs for QString and QVariant: v1, which is the default on
-Python 2, and the more natural v2, which is the only API supported by PySide.
-v2 is also the default for PyQt4 on Python 3.  IPython's code for the QtConsole
-uses v2, but you can still use any interface in your code, since the
-Qt frontend is in a different process.
-
-The default will be to import PyQt4 without configuration of the APIs, thus
-matching what most applications would expect. It will fall back to PySide if
-PyQt4 is unavailable.
+PyQt or PySide.  ``qt`` implies "use the latest version available", and it favors
+PyQt over PySide. To request a specific version, use ``qt5`` or ``qt6``. Note that
+Qt4 is not supported with the ``--gui`` switch (and has not been for some time now).
 
 If specified, IPython will respect the environment variable ``QT_API`` used
 by ETS.  ETS 4.0 also works with both PyQt4 and PySide, but it requires
 PyQt4 to use its v2 API.  So if ``QT_API=pyside`` PySide will be used,
 and if ``QT_API=pyqt`` then PyQt4 will be used *with the v2 API* for
 QString and QVariant, so ETS codes like MayaVi will also work with IPython.
 
 If you launch IPython in matplotlib mode with ``ipython --matplotlib=qt``,
 then IPython will ask matplotlib which Qt library to use (only if QT_API is
 *not set*), via the 'backend.qt4' rcParam.  If matplotlib is version 1.0.1 or
 older, then IPython will always use PyQt4 without setting the v2 APIs, since
 neither v2 PyQt nor PySide work.
 
 .. warning::
 
     Note that this means for ETS 4 to work with PyQt4, ``QT_API`` *must* be set
     to work with IPython's qt integration, because otherwise PyQt4 will be
     loaded in an incompatible mode.
 
     It also means that you must *not* have ``QT_API`` set if you want to
     use ``--gui=qt`` with code that requires PyQt4 API v1.
 
 
 .. _matplotlib_support:
 
 Plotting with matplotlib
 ========================
 
 matplotlib_ provides high quality 2D and 3D plotting for Python. matplotlib_
 can produce plots on screen using a variety of GUI toolkits, including Tk,
 PyGTK, PyQt4 and wxPython. It also provides a number of commands useful for
 scientific computing, all with a syntax compatible with that of the popular
 Matlab program.
 
 To start IPython with matplotlib support, use the ``--matplotlib`` switch. If
 IPython is already running, you can run the :magic:`matplotlib` magic.  If no
 arguments are given, IPython will automatically detect your choice of
 matplotlib backend.  You can also request a specific backend with
 ``%matplotlib backend``, where ``backend`` must be one of: 'tk', 'qt', 'wx',
 'gtk', 'osx'.  In the web notebook and Qt console, 'inline' is also a valid
 backend value, which produces static figures inlined inside the application
 window instead of matplotlib's interactive figures that live in separate
 windows.
 
 .. _interactive_demos:
 
 Interactive demos with IPython
 ==============================
 
 IPython ships with a basic system for running scripts interactively in
 sections, useful when presenting code to audiences. A few tags embedded
 in comments (so that the script remains valid Python code) divide a file
 into separate blocks, and the demo can be run one block at a time, with
 IPython printing (with syntax highlighting) the block before executing
 it, and returning to the interactive prompt after each block. The
 interactive namespace is updated after each block is run with the
 contents of the demo's namespace.
 
 This allows you to show a piece of code, run it and then execute
 interactively commands based on the variables just created. Once you
 want to continue, you simply execute the next block of the demo. The
 following listing shows the markup necessary for dividing a script into
 sections for execution as a demo:
 
 .. literalinclude:: ../../../examples/IPython Kernel/example-demo.py
     :language: python
 
 In order to run a file as a demo, you must first make a Demo object out
 of it. If the file is named myscript.py, the following code will make a
 demo::
 
     from IPython.lib.demo import Demo
 
     mydemo = Demo('myscript.py')
 
 This creates the mydemo object, whose blocks you run one at a time by
 simply calling the object with no arguments. Then call it to run each step
 of the demo::
 
     mydemo()
 
 Demo objects can be
 restarted, you can move forward or back skipping blocks, re-execute the
 last block, etc. See the :mod:`IPython.lib.demo` module and the
 :class:`~IPython.lib.demo.Demo` class for details.
 
 Limitations: These demos are limited to
 fairly simple uses. In particular, you cannot break up sections within
 indented code (loops, if statements, function definitions, etc.)
 Supporting something like this would basically require tracking the
 internal execution state of the Python interpreter, so only top-level
 divisions are allowed. If you want to be able to open an IPython
 instance at an arbitrary point in a program, you can use IPython's
 :ref:`embedding facilities <Embedding>`.
 
 .. include:: ../links.txt