Traceback improvements

Previously, error tracebacks for errors happening in code cells were showing a hash, the one used for compiling the Python AST:

In [1]: def foo():
...:     return 3 / 0
...:

In [2]: foo()
---------------------------------------------------------------------------
ZeroDivisionError                         Traceback (most recent call last)
<ipython-input-2-c19b6d9633cf> in <module>
----> 1 foo()

<ipython-input-1-1595a74c32d5> in foo()
    1 def foo():
----> 2     return 3 / 0
    3

ZeroDivisionError: division by zero

The error traceback is now correctly formatted, showing the cell number in which the error happened:

In [1]: def foo():
...:     return 3 / 0
...:

Input In [2]: foo()
---------------------------------------------------------------------------
ZeroDivisionError                         Traceback (most recent call last)
input In [2], in <module>
----> 1 foo()

Input In [1], in foo()
    1 def foo():
----> 2     return 3 / 0

ZeroDivisionError: division by zero

The Second on is the integration of the stack_data package; which provide smarter informations in traceback; in particular it will highlight the AST node where an error occurs which can help to quickly narrow down errors.

For example in the following snippet:

def foo(i):
    x = [[[0]]]
    return x[0][i][0]


def bar():
    return foo(0) + foo(
        1
    ) + foo(2)

Calling bar() would raise an IndexError on the return line of foo, IPython 8.0 is capable of telling you, where the index error occurs:

IndexError
Input In [2], in <module>
----> 1 bar()
        ^^^^^

Input In [1], in bar()
      6 def bar():
----> 7     return foo(0) + foo(
                            ^^^^
      8         1
         ^^^^^^^^
      9     ) + foo(2)
         ^^^^

Input In [1], in foo(i)
      1 def foo(i):
      2     x = [[[0]]]
----> 3     return x[0][i][0]
                   ^^^^^^^

Corresponding location marked here with ^ will show up highlighted in terminal and notebooks.

The Third, which is the most discreet but can have a high impact on productivity, a colon :: and line number is appended after a filename in traceback:

ZeroDivisionError               Traceback (most recent call last)
File ~/error.py:4, in <module>
      1 def f():
      2     1/0
----> 4 f()

File ~/error.py:2, in f()
      1 def f():
----> 2     1/0

Many terminal and editor have integrations allow to directly jump to the relevant file/line when this syntax is used.

Autosuggestons

Autosuggestion is a very useful feature available in fish, zsh, and prompt-toolkit.

Ptpython allows users to enable this feature in ptpython/config.py.

This feature allows users to accept autosuggestions with ctrl e, ctrl f, or right arrow as described below.

1. Start ipython

2. Run print("hello")

3. start typing print again to see the autosuggestion

4. Press ctrl-f, or ctrl-e, or right-arrow to accept the suggestion

You can also complete word by word:

1. Run def say_hello(): print("hello")

2. Start typing the first letter if def to see the autosuggestion

3. Press alt-f (or escape followed by f), to accept the first word of the suggestion

Importantly, this feature does not interfere with tab completion:

1. After running def say_hello(): print("hello"), press d

2. Press Tab to start tab completion

3A. Press Tab again to select the first option

3B. Press alt f (escape, f) to accept to accept the first word of the suggestion

3C. Press ctrl-f or ctrl-e to accept the entire suggestion

Currently, autosuggestions are only shown in the emacs or vi insert editing modes:

• The ctrl e, ctrl f, and alt f shortcuts work by default in emacs mode.
• To use these shortcuts in vi insert mode, you will have to create custom keybindings in your config.py.

Show pinfo information in ipdb using "?" and "??"

In IPDB, it is now possible to show the information about an object using "?" and "??", in much the same way it can be done when using the IPython prompt:

ipdb> partial?
Init signature: partial(self, /, *args, **kwargs)
Docstring:
partial(func, *args, **keywords) - new function with partial application
of the given arguments and keywords.
File:           ~/.pyenv/versions/3.8.6/lib/python3.8/functools.py
Type:           type
Subclasses:

Previously, pinfo or pinfo2 command had to be used for this purpose.

Autoreload 3 feature

Example: When an IPython session is ran with the 'autoreload' extension loaded, you will now have the option '3' to select which means the following:

1. replicate all functionality from option 2
2. autoload all new funcs/classes/enums/globals from the module when they are added
3. autoload all newly imported funcs/classes/enums/globals from external modules

Try %autoreload 3 in an IPython session after running %load_ext autoreload

For more information please see the following unit test : extensions/tests/test_autoreload.py:test_autoload_newly_added_objects

Auto formatting with black in the CLI

If black is installed in the same environment as IPython, terminal IPython will now by default reformat the code in the CLI when possible. You can disable this with --TerminalInteractiveShell.autoformatter=None.

This feature was present in 7.x but disabled by default.

History Range Glob feature

Previously, when using %history, users could specify either a range of sessions and lines, for example:

~8/1-~6/5   # see history from the first line of 8 sessions ago,
            # to the fifth line of 6 sessions ago.``

Or users could specify a glob pattern:

-g <pattern>  # glob ALL history for the specified pattern.

However users could not specify both.

If a user did specify both a range and a glob pattern, then the glob pattern would be used (globbing all history) and the range would be ignored.

With this enhancement, if a user specifies both a range and a glob pattern, then the glob pattern will be applied to the specified range of history.

Don't start a multi line cell with sunken parenthesis

From now on IPython will not ask for the next line of input when given a single line with more closing than opening brackets. For example, this means that if you (mis)type ]] instead of [], a SyntaxError will show up, instead of the ...: prompt continuation.

IPython shell for ipdb interact

The ipdb interact starts an IPython shell instead of Python's built-in code.interact().

Automatic Vi prompt stripping

When pasting code into IPython, it will strip the leading prompt characters if there are any. For example, you can paste the following code into the console - it will still work, even though each line is prefixed with prompts (In, Out):

In [1]: 2 * 2 == 4
Out[1]: True

In [2]: print("This still works as pasted")

Previously, this was not the case for the Vi-mode prompts:

In [1]: [ins] In [13]: 2 * 2 == 4
   ...: Out[13]: True
   ...:
  File "<ipython-input-1-727bb88eaf33>", line 1
    [ins] In [13]: 2 * 2 == 4
          ^
SyntaxError: invalid syntax

This is now fixed, and Vi prompt prefixes - [ins] and [nav] - are skipped just as the normal In would be.

IPython shell can be started in the Vi mode using ipython --TerminalInteractiveShell.editing_mode=vi, You should be able to change mode dynamically with %config TerminalInteractiveShell.editing_mode='vi'

Empty History Ranges

A number of magics that take history ranges can now be used with an empty range. These magics are:

• %save
• %load
• %pastebin
• %pycat

Using them this way will make them take the history of the current session up to the point of the magic call (such that the magic itself will not be included).

Therefore it is now possible to save the whole history to a file using simple %save <filename>, load and edit it using %load (makes for a nice usage when followed with :kbd:`F2`), send it to dpaste.org using %pastebin, or view the whole thing syntax-highlighted with a single %pycat.

Windows time-implementation: Switch to process_time

Timing for example with %%time on windows is based on time.perf_counter. This is at the end the same as W-All. To be a bit tighter to linux one could change to time.process_time instead. Thus for example one would no longer count periods of sleep and further.

Miscellaneous

• Non-text formatters are not disabled in terminal which should simplify writing extension displaying images or other mimetypes supporting terminals. :ghpull:`12315`
• It is now possible to automatically insert matching brackets in Terminal IPython using the TerminalInteractiveShell.auto_match=True option. :ghpull:`12586`
• We are thinking of deprecating the current %%javascript magic in favor of a better replacement. See :ghpull:`13376`
• %time uses process_time instead of perf_counter, see :ghpull:`12984`
• ~ is now expanded when part of a path in most magics :ghpull:`13385`
• %/%%timeit magic now adds comma every thousands to make reading long number easier :ghpull:`13379`
• "info" messages can now be customised to hide some fields :ghpull:`13343`
• collections.UserList now pretty-prints :ghpull:`13320`
• The debugger now have a persistent history, which should make it less annoying to retype commands :ghpull:`13246`
• !pip !conda !cd or !ls are likely doing the wrong thing, we now warn users if they use it. :ghpull:`12954`
• make %precision work for numpy.float64 type :ghpull:`12902`

Re-added support for XDG config directories

XDG support through the years did come an go, there is a tension between having identical location in all platforms to have simple instructions. After initial failure a couple of years ago IPython was modified to automatically migrate XDG config files back into ~/.ipython, the migration code has now been removed. And IPython now check the XDG locations, so if you _manually_ move your config files to your preferred location, IPython will not move them back.