Use 'is' to compare with None

Issues were detected by PyCharm Community Edition 3.4.

IPython/lib/display.py

@@ -1,533 +1,533 b''
 """Various display related classes.
 
 Authors : MinRK, gregcaporaso, dannystaple
 """
 from os.path import exists, isfile, splitext, abspath, join, isdir
 from os import walk, sep
 
 from IPython.core.display import DisplayObject
 
 __all__ = ['Audio', 'IFrame', 'YouTubeVideo', 'VimeoVideo', 'ScribdDocument',
            'FileLink', 'FileLinks']
 
 
 class Audio(DisplayObject):
     """Create an audio object.
 
     When this object is returned by an input cell or passed to the
     display function, it will result in Audio controls being displayed
     in the frontend (only works in the notebook).
 
     Parameters
     ----------
     data : numpy array, list, unicode, str or bytes
         Can be one of
 
           * Numpy 1d array containing the desired waveform (mono)
           * Numpy 2d array containing waveforms for each channel.
             Shape=(NCHAN, NSAMPLES). For the standard channel order, see
             http://msdn.microsoft.com/en-us/library/windows/hardware/dn653308(v=vs.85).aspx
           * List of float or integer representing the waveform (mono)
           * String containing the filename
           * Bytestring containing raw PCM data or
           * URL pointing to a file on the web.
 
         If the array option is used the waveform will be normalized.
 
         If a filename or url is used the format support will be browser
         dependent.
     url : unicode
         A URL to download the data from.
     filename : unicode
         Path to a local file to load the data from.
     embed : boolean
         Should the image data be embedded using a data URI (True) or should
         the original source be referenced. Set this to True if you want the
         audio to playable later with no internet connection in the notebook.
 
         Default is `True`, unless the keyword argument `url` is set, then
         default value is `False`.
     rate : integer
         The sampling rate of the raw data.
         Only required when data parameter is being used as an array
     autoplay : bool
         Set to True if the audio should immediately start playing.
         Default is `False`.
 
     Examples
     --------
     ::
 
         # Generate a sound
         import numpy as np
         framerate = 44100
         t = np.linspace(0,5,framerate*5)
         data = np.sin(2*np.pi*220*t) + np.sin(2*np.pi*224*t))
         Audio(data,rate=framerate)
 
         # Can also do stereo or more channels
         dataleft = np.sin(2*np.pi*220*t)
         dataright = np.sin(2*np.pi*224*t)
         Audio([dataleft, dataright],rate=framerate)
 
         Audio("http://www.nch.com.au/acm/8k16bitpcm.wav")  # From URL
         Audio(url="http://www.w3schools.com/html/horse.ogg")
 
         Audio('/path/to/sound.wav')  # From file
         Audio(filename='/path/to/sound.ogg')
 
         Audio(b'RAW_WAV_DATA..)  # From bytes
         Audio(data=b'RAW_WAV_DATA..)
 
     """
     _read_flags = 'rb'
 
     def __init__(self, data=None, filename=None, url=None, embed=None, rate=None, autoplay=False):
         if filename is None and url is None and data is None:
             raise ValueError("No image data found. Expecting filename, url, or data.")
         if embed is False and url is None:
             raise ValueError("No url found. Expecting url when embed=False")
 
         if url is not None and embed is not True:
             self.embed = False
         else:
             self.embed = True
         self.autoplay = autoplay
         super(Audio, self).__init__(data=data, url=url, filename=filename)
 
         if self.data is not None and not isinstance(self.data, bytes):
             self.data = self._make_wav(data,rate)
 
     def reload(self):
         """Reload the raw data from file or URL."""
         import mimetypes
         if self.embed:
             super(Audio, self).reload()
 
         if self.filename is not None:
             self.mimetype = mimetypes.guess_type(self.filename)[0]
         elif self.url is not None:
             self.mimetype = mimetypes.guess_type(self.url)[0]
         else:
             self.mimetype = "audio/wav"
 
     def _make_wav(self, data, rate):
         """ Transform a numpy array to a PCM bytestring """
         import struct
         from io import BytesIO
         import wave
 
         try:
             import numpy as np
 
             data = np.array(data, dtype=float)
             if len(data.shape) == 1:
                 nchan = 1
             elif len(data.shape) == 2:
                 # In wave files,channels are interleaved. E.g.,
                 # "L1R1L2R2..." for stereo. See
                 # http://msdn.microsoft.com/en-us/library/windows/hardware/dn653308(v=vs.85).aspx
                 # for channel ordering
                 nchan = data.shape[0]
                 data = data.T.ravel()
             else:
                 raise ValueError('Array audio input must be a 1D or 2D array')
             scaled = np.int16(data/np.max(np.abs(data))*32767).tolist()
         except ImportError:
             # check that it is a "1D" list
             idata = iter(data)  # fails if not an iterable
             try:
                 iter(idata.next())
                 raise TypeError('Only lists of mono audio are '
                     'supported if numpy is not installed')
             except TypeError:
                 # this means it's not a nested list, which is what we want
                 pass
             maxabsvalue = float(max([abs(x) for x in data]))
             scaled = [int(x/maxabsvalue*32767) for x in data]
             nchan = 1
 
         fp = BytesIO()
         waveobj = wave.open(fp,mode='wb')
         waveobj.setnchannels(nchan)
         waveobj.setframerate(rate)
         waveobj.setsampwidth(2)
         waveobj.setcomptype('NONE','NONE')
         waveobj.writeframes(b''.join([struct.pack('<h',x) for x in scaled]))
         val = fp.getvalue()
         waveobj.close()
 
         return val
 
     def _data_and_metadata(self):
         """shortcut for returning metadata with url information, if defined"""
         md = {}
         if self.url:
             md['url'] = self.url
         if md:
             return self.data, md
         else:
             return self.data
 
     def _repr_html_(self):
         src = """
                 <audio controls="controls" {autoplay}>
                     <source src="{src}" type="{type}" />
                     Your browser does not support the audio element.
                 </audio>
               """
         return src.format(src=self.src_attr(),type=self.mimetype, autoplay=self.autoplay_attr())
 
     def src_attr(self):
         import base64
         if self.embed and (self.data is not None):
             data = base64=base64.b64encode(self.data).decode('ascii')
             return """data:{type};base64,{base64}""".format(type=self.mimetype,
                                                             base64=data)
         elif self.url is not None:
             return self.url
         else:
             return ""
 
     def autoplay_attr(self):
         if(self.autoplay):
             return 'autoplay="autoplay"'
         else:
             return ''
 
 class IFrame(object):
     """
     Generic class to embed an iframe in an IPython notebook
     """
 
     iframe = """
         <iframe
             width="{width}"
             height="{height}"
             src="{src}{params}"
             frameborder="0"
             allowfullscreen
         ></iframe>
         """
 
     def __init__(self, src, width, height, **kwargs):
         self.src = src
         self.width = width
         self.height = height
         self.params = kwargs
 
     def _repr_html_(self):
         """return the embed iframe"""
         if self.params:
             try:
                 from urllib.parse import urlencode # Py 3
             except ImportError:
                 from urllib import urlencode
             params = "?" + urlencode(self.params)
         else:
             params = ""
         return self.iframe.format(src=self.src,
                                   width=self.width,
                                   height=self.height,
                                   params=params)
 
 class YouTubeVideo(IFrame):
     """Class for embedding a YouTube Video in an IPython session, based on its video id.
 
     e.g. to embed the video from https://www.youtube.com/watch?v=foo , you would
     do::
 
         vid = YouTubeVideo("foo")
         display(vid)
 
     To start from 30 seconds::
 
         vid = YouTubeVideo("abc", start=30)
         display(vid)
 
     To calculate seconds from time as hours, minutes, seconds use
     :class:`datetime.timedelta`::
 
         start=int(timedelta(hours=1, minutes=46, seconds=40).total_seconds())
 
     Other parameters can be provided as documented at
     https://developers.google.com/youtube/player_parameters#parameter-subheader
     """
 
     def __init__(self, id, width=400, height=300, **kwargs):
         src = "https://www.youtube.com/embed/{0}".format(id)
         super(YouTubeVideo, self).__init__(src, width, height, **kwargs)
 
 class VimeoVideo(IFrame):
     """
     Class for embedding a Vimeo video in an IPython session, based on its video id.
     """
 
     def __init__(self, id, width=400, height=300, **kwargs):
         src="https://player.vimeo.com/video/{0}".format(id)
         super(VimeoVideo, self).__init__(src, width, height, **kwargs)
 
 class ScribdDocument(IFrame):
     """
     Class for embedding a Scribd document in an IPython session
 
     Use the start_page params to specify a starting point in the document
     Use the view_mode params to specify display type one off scroll | slideshow | book
 
     e.g to Display Wes' foundational paper about PANDAS in book mode from page 3
 
     ScribdDocument(71048089, width=800, height=400, start_page=3, view_mode="book")
     """
 
     def __init__(self, id, width=400, height=300, **kwargs):
         src="https://www.scribd.com/embeds/{0}/content".format(id)
         super(ScribdDocument, self).__init__(src, width, height, **kwargs)
 
 class FileLink(object):
     """Class for embedding a local file link in an IPython session, based on path
 
     e.g. to embed a link that was generated in the IPython notebook as my/data.txt
 
     you would do::
 
         local_file = FileLink("my/data.txt")
         display(local_file)
 
     or in the HTML notebook, just::
 
         FileLink("my/data.txt")
     """
 
     html_link_str = "<a href='%s' target='_blank'>%s</a>"
 
     def __init__(self,
                  path,
                  url_prefix='',
                  result_html_prefix='',
                  result_html_suffix='<br>'):
         """
         Parameters
         ----------
         path : str
             path to the file or directory that should be formatted
         directory_prefix : str
             prefix to be prepended to all files to form a working link [default:
             'files']
         result_html_prefix : str
             text to append to beginning to link [default: none]
         result_html_suffix : str
             text to append at the end of link [default: '<br>']
         """
         if isdir(path):
             raise ValueError("Cannot display a directory using FileLink. "
               "Use FileLinks to display '%s'." % path)
         self.path = path
         self.url_prefix = url_prefix
         self.result_html_prefix = result_html_prefix
         self.result_html_suffix = result_html_suffix
 
     def _format_path(self):
         fp = ''.join([self.url_prefix,self.path])
         return ''.join([self.result_html_prefix,
                         self.html_link_str % (fp, self.path),
                         self.result_html_suffix])
 
     def _repr_html_(self):
         """return html link to file
         """
         if not exists(self.path):
             return ("Path (<tt>%s</tt>) doesn't exist. "
                     "It may still be in the process of "
                     "being generated, or you may have the "
                     "incorrect path." % self.path)
 
         return self._format_path()
 
     def __repr__(self):
         """return absolute path to file
         """
         return abspath(self.path)
 
 class FileLinks(FileLink):
     """Class for embedding local file links in an IPython session, based on path
 
     e.g. to embed links to files that were generated in the IPython notebook
     under ``my/data``, you would do::
 
         local_files = FileLinks("my/data")
         display(local_files)
 
     or in the HTML notebook, just::
 
         FileLinks("my/data")
     """
     def __init__(self,
                  path,
                  url_prefix='',
                  included_suffixes=None,
                  result_html_prefix='',
                  result_html_suffix='<br>',
                  notebook_display_formatter=None,
                  terminal_display_formatter=None):
         """
         See :class:`FileLink` for the ``path``, ``url_prefix``,
         ``result_html_prefix`` and ``result_html_suffix`` parameters.
 
         included_suffixes : list
           Filename suffixes to include when formatting output [default: include
           all files]
 
         notebook_display_formatter : function
           Used to format links for display in the notebook. See discussion of
           formatter functions below.
 
         terminal_display_formatter : function
           Used to format links for display in the terminal. See discussion of
           formatter functions below.
 
         Formatter functions must be of the form::
 
             f(dirname, fnames, included_suffixes)
 
         dirname : str
           The name of a directory
         fnames : list
           The files in that directory
         included_suffixes : list
           The file suffixes that should be included in the output (passing None
           meansto include all suffixes in the output in the built-in formatters)
 
         The function should return a list of lines that will be printed in the
         notebook (if passing notebook_display_formatter) or the terminal (if
         passing terminal_display_formatter). This function is iterated over for
         each directory in self.path. Default formatters are in place, can be
         passed here to support alternative formatting.
 
         """
         if isfile(path):
             raise ValueError("Cannot display a file using FileLinks. "
               "Use FileLink to display '%s'." % path)
         self.included_suffixes = included_suffixes
         # remove trailing slashs for more consistent output formatting
         path = path.rstrip('/')
 
         self.path = path
         self.url_prefix = url_prefix
         self.result_html_prefix = result_html_prefix
         self.result_html_suffix = result_html_suffix
 
         self.notebook_display_formatter = \
              notebook_display_formatter or self._get_notebook_display_formatter()
         self.terminal_display_formatter = \
              terminal_display_formatter or self._get_terminal_display_formatter()
 
     def _get_display_formatter(self,
                                dirname_output_format,
                                fname_output_format,
                                fp_format,
                                fp_cleaner=None):
         """ generate built-in formatter function
 
            this is used to define both the notebook and terminal built-in
             formatters as they only differ by some wrapper text for each entry
 
            dirname_output_format: string to use for formatting directory
             names, dirname will be substituted for a single "%s" which
             must appear in this string
            fname_output_format: string to use for formatting file names,
             if a single "%s" appears in the string, fname will be substituted
             if two "%s" appear in the string, the path to fname will be
              substituted for the first and fname will be substituted for the
              second
            fp_format: string to use for formatting filepaths, must contain
             exactly two "%s" and the dirname will be subsituted for the first
             and fname will be substituted for the second
         """
         def f(dirname, fnames, included_suffixes=None):
             result = []
             # begin by figuring out which filenames, if any,
             # are going to be displayed
             display_fnames = []
             for fname in fnames:
                 if (isfile(join(dirname,fname)) and
-                       (included_suffixes == None or
+                       (included_suffixes is None or
                         splitext(fname)[1] in included_suffixes)):
                       display_fnames.append(fname)
 
             if len(display_fnames) == 0:
                 # if there are no filenames to display, don't print anything
                 # (not even the directory name)
                 pass
             else:
                 # otherwise print the formatted directory name followed by
                 # the formatted filenames
                 dirname_output_line = dirname_output_format % dirname
                 result.append(dirname_output_line)
                 for fname in display_fnames:
                     fp = fp_format % (dirname,fname)
                     if fp_cleaner is not None:
                         fp = fp_cleaner(fp)
                     try:
                         # output can include both a filepath and a filename...
                         fname_output_line = fname_output_format % (fp, fname)
                     except TypeError:
                         # ... or just a single filepath
                         fname_output_line = fname_output_format % fname
                     result.append(fname_output_line)
             return result
         return f
 
     def _get_notebook_display_formatter(self,
                                         spacer="&nbsp;&nbsp;"):
         """ generate function to use for notebook formatting
         """
         dirname_output_format = \
          self.result_html_prefix + "%s/" + self.result_html_suffix
         fname_output_format = \
          self.result_html_prefix + spacer + self.html_link_str + self.result_html_suffix
         fp_format = self.url_prefix + '%s/%s'
         if sep == "\\":
             # Working on a platform where the path separator is "\", so
             # must convert these to "/" for generating a URI
             def fp_cleaner(fp):
                 # Replace all occurences of backslash ("\") with a forward
                 # slash ("/") - this is necessary on windows when a path is
                 # provided as input, but we must link to a URI
                 return fp.replace('\\','/')
         else:
             fp_cleaner = None
 
         return self._get_display_formatter(dirname_output_format,
                                            fname_output_format,
                                            fp_format,
                                            fp_cleaner)
 
     def _get_terminal_display_formatter(self,
                                         spacer="  "):
         """ generate function to use for terminal formatting
         """
         dirname_output_format = "%s/"
         fname_output_format = spacer + "%s"
         fp_format = '%s/%s'
 
         return self._get_display_formatter(dirname_output_format,
                                            fname_output_format,
                                            fp_format)
 
     def _format_path(self):
         result_lines = []
         walked_dir = list(walk(self.path))
         walked_dir.sort()
         for dirname, subdirs, fnames in walked_dir:
             result_lines += self.notebook_display_formatter(dirname, fnames, self.included_suffixes)
         return '\n'.join(result_lines)
 
     def __repr__(self):
         """return newline-separated absolute paths
         """
         result_lines = []
         walked_dir = list(walk(self.path))
         walked_dir.sort()
         for dirname, subdirs, fnames in walked_dir:
             result_lines += self.terminal_display_formatter(dirname, fnames, self.included_suffixes)
         return '\n'.join(result_lines)

IPython/qt/console/magic_helper.py

@@ -1,213 +1,213 b''
 """MagicHelper - dockable widget showing magic commands for the MainWindow
 """
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License. 
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 # stdlib imports
 import json
 import re
 import sys
 
 # System library imports
 from IPython.external.qt import QtGui,QtCore
 
 from IPython.core.magic import magic_escapes
 
 class MagicHelper(QtGui.QDockWidget):
     """MagicHelper - dockable widget for convenient search and running of
                      magic command for IPython QtConsole.
     """
 
     #---------------------------------------------------------------------------
     # signals
     #---------------------------------------------------------------------------
 
     pasteRequested = QtCore.Signal(str, name = 'pasteRequested')
     """This signal is emitted when user wants to paste selected magic 
        command into the command line.
     """
 
     runRequested = QtCore.Signal(str, name = 'runRequested')
     """This signal is emitted when user wants to execute selected magic command
     """
 
     readyForUpdate = QtCore.Signal(name = 'readyForUpdate')
     """This signal is emitted when MagicHelper is ready to be populated.
        Since kernel querying mechanisms are out of scope of this class,
        it expects its owner to invoke MagicHelper.populate_magic_helper()
        as a reaction on this event.
     """
 
     #---------------------------------------------------------------------------
     # constructor
     #---------------------------------------------------------------------------
 
     def __init__(self, name, parent):
         super(MagicHelper, self).__init__(name, parent)
 
         self.data = None
 
         class MinListWidget(QtGui.QListWidget):
             """Temp class to overide the default QListWidget size hint
                in order to make MagicHelper narrow
             """
             def sizeHint(self):
                 s = QtCore.QSize()
                 s.setHeight(super(MinListWidget,self).sizeHint().height())
                 s.setWidth(self.sizeHintForColumn(0))
                 return s
 
         # construct content
         self.frame = QtGui.QFrame()
         self.search_label = QtGui.QLabel("Search:")
         self.search_line = QtGui.QLineEdit()
         self.search_class = QtGui.QComboBox()
         self.search_list = MinListWidget()
         self.paste_button = QtGui.QPushButton("Paste")
         self.run_button = QtGui.QPushButton("Run")
         
         # layout all the widgets
         main_layout = QtGui.QVBoxLayout()
         search_layout = QtGui.QHBoxLayout()
         search_layout.addWidget(self.search_label)
         search_layout.addWidget(self.search_line, 10)
         main_layout.addLayout(search_layout)
         main_layout.addWidget(self.search_class)
         main_layout.addWidget(self.search_list, 10)
         action_layout = QtGui.QHBoxLayout()
         action_layout.addWidget(self.paste_button)
         action_layout.addWidget(self.run_button)
         main_layout.addLayout(action_layout)
 
         self.frame.setLayout(main_layout)
         self.setWidget(self.frame)
 
         # connect all the relevant signals to handlers
         self.visibilityChanged[bool].connect( self._update_magic_helper )
         self.search_class.activated[int].connect( 
             self.class_selected
         )
         self.search_line.textChanged[str].connect(
             self.search_changed
         )
         self.search_list.itemDoubleClicked[QtGui.QListWidgetItem].connect(
             self.paste_requested
         )
         self.paste_button.clicked[bool].connect(
             self.paste_requested
         )
         self.run_button.clicked[bool].connect(
             self.run_requested
         )
 
     #---------------------------------------------------------------------------
     # implementation
     #---------------------------------------------------------------------------
 
     def _update_magic_helper(self, visible):
         """Start update sequence. 
            This method is called when MagicHelper becomes visible. It clears
            the content and emits readyForUpdate signal. The owner of the 
            instance is expected to invoke populate_magic_helper() when magic
            info is available.
         """
-        if not visible or self.data != None:
+        if not visible or self.data is not None:
             return
         self.data = {}
         self.search_class.clear()
         self.search_class.addItem("Populating...")
         self.search_list.clear()
         self.readyForUpdate.emit()
 
     def populate_magic_helper(self, data):
         """Expects data returned by lsmagics query from kernel.
            Populates the search_class and search_list with relevant items.
         """
         self.search_class.clear()
         self.search_list.clear()
                 
         self.data = json.loads(
             data['data'].get('application/json', {})
         )
         
         self.search_class.addItem('All Magics', 'any')
         classes = set()
 
         for mtype in sorted(self.data):
             subdict = self.data[mtype]
             for name in sorted(subdict):
                 classes.add(subdict[name])
 
         for cls in sorted(classes):
             label = re.sub("([a-zA-Z]+)([A-Z][a-z])","\g<1> \g<2>", cls)
             self.search_class.addItem(label, cls)
 
         self.filter_magic_helper('.', 'any')
 
     def class_selected(self, index):
         """Handle search_class selection changes
         """
         item = self.search_class.itemData(index)
         regex = self.search_line.text()
         self.filter_magic_helper(regex = regex, cls = item)
 
     def search_changed(self, search_string):
         """Handle search_line text changes.
            The text is interpreted as a regular expression
         """
         item = self.search_class.itemData(
             self.search_class.currentIndex()
         )
         self.filter_magic_helper(regex = search_string, cls = item)
 
     def _get_current_search_item(self, item = None):
         """Retrieve magic command currently selected in the search_list
         """
         text = None
         if not isinstance(item, QtGui.QListWidgetItem):
             item = self.search_list.currentItem()        
         text = item.text()
         return text
 
     def paste_requested(self, item = None):
         """Emit pasteRequested signal with currently selected item text
         """
         text = self._get_current_search_item(item)
-        if text != None:
+        if text is not None:
             self.pasteRequested.emit(text)
 
     def run_requested(self, item = None):
         """Emit runRequested signal with currently selected item text
         """
         text = self._get_current_search_item(item)
-        if text != None:            
+        if text is not None:
             self.runRequested.emit(text)
 
     def filter_magic_helper(self, regex, cls):
         """Update search_list with magic commands whose text match
            regex and class match cls.
            If cls equals 'any' - any class matches.
         """
-        if regex == "" or regex == None:
+        if regex == "" or regex is None:
             regex = '.'
-        if cls == None:
+        if cls is None:
             cls = 'any'
 
         self.search_list.clear()
         for mtype in sorted(self.data):
             subdict = self.data[mtype]
             prefix = magic_escapes[mtype]
 
             for name in sorted(subdict):
                 mclass = subdict[name]
                 pmagic = prefix + name
 
                 if (re.match(regex, name) or re.match(regex, pmagic)) and \
                    (cls == 'any' or cls == mclass): 
                     self.search_list.addItem(pmagic)
 

IPython/qt/console/mainwindow.py

@@ -1,928 +1,928 b''
 """The Qt MainWindow for the QtConsole
 
 This is a tabbed pseudo-terminal of IPython sessions, with a menu bar for
 common actions.
 """
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License. 
 
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 # stdlib imports
 import json
 import re
 import sys
 import webbrowser
 from threading import Thread
 
 # System library imports
 from IPython.external.qt import QtGui,QtCore
 
 from IPython.core.magic import magic_escapes
 
 def background(f):
     """call a function in a simple thread, to prevent blocking"""
     t = Thread(target=f)
     t.start()
     return t
 
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
 
 class MainWindow(QtGui.QMainWindow):
 
     #---------------------------------------------------------------------------
     # 'object' interface
     #---------------------------------------------------------------------------
 
     def __init__(self, app,
                     confirm_exit=True,
                     new_frontend_factory=None, slave_frontend_factory=None,
                 ):
         """ Create a tabbed MainWindow for managing IPython FrontendWidgets
         
         Parameters
         ----------
         
         app : reference to QApplication parent
         confirm_exit : bool, optional
             Whether we should prompt on close of tabs
         new_frontend_factory : callable
             A callable that returns a new IPythonWidget instance, attached to
             its own running kernel.
         slave_frontend_factory : callable
             A callable that takes an existing IPythonWidget, and  returns a new 
             IPythonWidget instance, attached to the same kernel.
         """
 
         super(MainWindow, self).__init__()
         self._kernel_counter = 0
         self._app = app
         self.confirm_exit = confirm_exit
         self.new_frontend_factory = new_frontend_factory
         self.slave_frontend_factory = slave_frontend_factory
 
         self.tab_widget = QtGui.QTabWidget(self)
         self.tab_widget.setDocumentMode(True)
         self.tab_widget.setTabsClosable(True)
         self.tab_widget.tabCloseRequested[int].connect(self.close_tab)
 
         self.setCentralWidget(self.tab_widget)
         # hide tab bar at first, since we have no tabs:
         self.tab_widget.tabBar().setVisible(False)
         # prevent focus in tab bar
         self.tab_widget.setFocusPolicy(QtCore.Qt.NoFocus)
 
     def update_tab_bar_visibility(self):
         """ update visibility of the tabBar depending of the number of tab
 
         0 or 1 tab, tabBar hidden
         2+ tabs, tabBar visible
 
         send a self.close if number of tab ==0
 
         need to be called explicitly, or be connected to tabInserted/tabRemoved
         """
         if self.tab_widget.count() <= 1:
             self.tab_widget.tabBar().setVisible(False)
         else:
             self.tab_widget.tabBar().setVisible(True)
         if self.tab_widget.count()==0 :
             self.close()
 
     @property
     def next_kernel_id(self):
         """constantly increasing counter for kernel IDs"""
         c = self._kernel_counter
         self._kernel_counter += 1
         return c
 
     @property
     def active_frontend(self):
         return self.tab_widget.currentWidget()
     
     def create_tab_with_new_frontend(self):
         """create a new frontend and attach it to a new tab"""
         widget = self.new_frontend_factory()
         self.add_tab_with_frontend(widget)
     
     def create_tab_with_current_kernel(self):
         """create a new frontend attached to the same kernel as the current tab"""
         current_widget = self.tab_widget.currentWidget()
         current_widget_index = self.tab_widget.indexOf(current_widget)
         current_widget_name = self.tab_widget.tabText(current_widget_index)
         widget = self.slave_frontend_factory(current_widget)
         if 'slave' in current_widget_name:
             # don't keep stacking slaves
             name = current_widget_name
         else:
             name = '(%s) slave' % current_widget_name
         self.add_tab_with_frontend(widget,name=name)
 
     def close_tab(self,current_tab):
         """ Called when you need to try to close a tab.
 
         It takes the number of the tab to be closed as argument, or a reference
         to the widget inside this tab
         """
 
         # let's be sure "tab" and "closing widget" are respectively the index
         # of the tab to close and a reference to the frontend to close
         if type(current_tab) is not int :
             current_tab = self.tab_widget.indexOf(current_tab)
         closing_widget=self.tab_widget.widget(current_tab)
 
 
         # when trying to be closed, widget might re-send a request to be
         # closed again, but will be deleted when event will be processed. So
         # need to check that widget still exists and skip if not. One example
         # of this is when 'exit' is sent in a slave tab. 'exit' will be
         # re-sent by this function on the master widget, which ask all slave
         # widgets to exit
-        if closing_widget==None:
+        if closing_widget is None:
             return
 
         #get a list of all slave widgets on the same kernel.
         slave_tabs = self.find_slave_widgets(closing_widget)
 
         keepkernel = None #Use the prompt by default
         if hasattr(closing_widget,'_keep_kernel_on_exit'): #set by exit magic
             keepkernel = closing_widget._keep_kernel_on_exit
             # If signal sent by exit magic (_keep_kernel_on_exit, exist and not None)
             # we set local slave tabs._hidden to True to avoid prompting for kernel
             # restart when they get the signal. and then "forward" the 'exit'
             # to the main window
             if keepkernel is not None:
                 for tab in slave_tabs:
                     tab._hidden = True
                 if closing_widget in slave_tabs:
                     try :
                         self.find_master_tab(closing_widget).execute('exit')
                     except AttributeError:
                         self.log.info("Master already closed or not local, closing only current tab")
                         self.tab_widget.removeTab(current_tab)
                     self.update_tab_bar_visibility()
                     return
 
         kernel_client = closing_widget.kernel_client
         kernel_manager = closing_widget.kernel_manager
 
         if keepkernel is None and not closing_widget._confirm_exit:
             # don't prompt, just terminate the kernel if we own it
             # or leave it alone if we don't
             keepkernel = closing_widget._existing
         if keepkernel is None: #show prompt
             if kernel_client and kernel_client.channels_running:
                 title = self.window().windowTitle()
                 cancel = QtGui.QMessageBox.Cancel
                 okay = QtGui.QMessageBox.Ok
                 if closing_widget._may_close:
                     msg = "You are closing the tab : "+'"'+self.tab_widget.tabText(current_tab)+'"'
                     info = "Would you like to quit the Kernel and close all attached Consoles as well?"
                     justthis = QtGui.QPushButton("&No, just this Tab", self)
                     justthis.setShortcut('N')
                     closeall = QtGui.QPushButton("&Yes, close all", self)
                     closeall.setShortcut('Y')
                     # allow ctrl-d ctrl-d exit, like in terminal
                     closeall.setShortcut('Ctrl+D')
                     box = QtGui.QMessageBox(QtGui.QMessageBox.Question,
                                             title, msg)
                     box.setInformativeText(info)
                     box.addButton(cancel)
                     box.addButton(justthis, QtGui.QMessageBox.NoRole)
                     box.addButton(closeall, QtGui.QMessageBox.YesRole)
                     box.setDefaultButton(closeall)
                     box.setEscapeButton(cancel)
                     pixmap = QtGui.QPixmap(self._app.icon.pixmap(QtCore.QSize(64,64)))
                     box.setIconPixmap(pixmap)
                     reply = box.exec_()
                     if reply == 1: # close All
                         for slave in slave_tabs:
                             background(slave.kernel_client.stop_channels)
                             self.tab_widget.removeTab(self.tab_widget.indexOf(slave))
                         closing_widget.execute("exit")
                         self.tab_widget.removeTab(current_tab)
                         background(kernel_client.stop_channels)
                     elif reply == 0: # close Console
                         if not closing_widget._existing:
                             # Have kernel: don't quit, just close the tab
                             closing_widget.execute("exit True")
                         self.tab_widget.removeTab(current_tab)
                         background(kernel_client.stop_channels)
                 else:
                     reply = QtGui.QMessageBox.question(self, title,
                         "Are you sure you want to close this Console?"+
                         "\nThe Kernel and other Consoles will remain active.",
                         okay|cancel,
                         defaultButton=okay
                         )
                     if reply == okay:
                         self.tab_widget.removeTab(current_tab)
         elif keepkernel: #close console but leave kernel running (no prompt)
             self.tab_widget.removeTab(current_tab)
             background(kernel_client.stop_channels)
         else: #close console and kernel (no prompt)
             self.tab_widget.removeTab(current_tab)
             if kernel_client and kernel_client.channels_running:
                 for slave in slave_tabs:
                     background(slave.kernel_client.stop_channels)
                     self.tab_widget.removeTab(self.tab_widget.indexOf(slave))
                 if kernel_manager:
                     kernel_manager.shutdown_kernel()
                 background(kernel_client.stop_channels)
         
         self.update_tab_bar_visibility()
 
     def add_tab_with_frontend(self,frontend,name=None):
         """ insert a tab with a given frontend in the tab bar, and give it a name
 
         """
         if not name:
             name = 'kernel %i' % self.next_kernel_id
         self.tab_widget.addTab(frontend,name)
         self.update_tab_bar_visibility()
         self.make_frontend_visible(frontend)
         frontend.exit_requested.connect(self.close_tab)
 
     def next_tab(self):
         self.tab_widget.setCurrentIndex((self.tab_widget.currentIndex()+1))
 
     def prev_tab(self):
         self.tab_widget.setCurrentIndex((self.tab_widget.currentIndex()-1))
 
     def make_frontend_visible(self,frontend):
         widget_index=self.tab_widget.indexOf(frontend)
         if widget_index > 0 :
             self.tab_widget.setCurrentIndex(widget_index)
 
     def find_master_tab(self,tab,as_list=False):
         """
         Try to return the frontend that owns the kernel attached to the given widget/tab.
 
             Only finds frontend owned by the current application. Selection
             based on port of the kernel might be inaccurate if several kernel
             on different ip use same port number.
 
             This function does the conversion tabNumber/widget if needed.
             Might return None if no master widget (non local kernel)
             Will crash IPython if more than 1 masterWidget
 
             When asList set to True, always return a list of widget(s) owning
             the kernel. The list might be empty or containing several Widget.
         """
 
         #convert from/to int/richIpythonWidget if needed
         if isinstance(tab, int):
             tab = self.tab_widget.widget(tab)
         km=tab.kernel_client
 
         #build list of all widgets
         widget_list = [self.tab_widget.widget(i) for i in range(self.tab_widget.count())]
 
         # widget that are candidate to be the owner of the kernel does have all the same port of the curent widget
         # And should have a _may_close attribute
         filtered_widget_list = [ widget for widget in widget_list if
                                 widget.kernel_client.connection_file == km.connection_file and
                                 hasattr(widget,'_may_close') ]
         # the master widget is the one that may close the kernel
         master_widget= [ widget for widget in filtered_widget_list if widget._may_close]
         if as_list:
             return master_widget
         assert(len(master_widget)<=1 )
         if len(master_widget)==0:
             return None
 
         return master_widget[0]
 
     def find_slave_widgets(self,tab):
         """return all the frontends that do not own the kernel attached to the given widget/tab.
 
             Only find frontends owned by the current application. Selection
             based on connection file of the kernel.
 
             This function does the conversion tabNumber/widget if needed.
         """
         #convert from/to int/richIpythonWidget if needed
         if isinstance(tab, int):
             tab = self.tab_widget.widget(tab)
         km=tab.kernel_client
 
         #build list of all widgets
         widget_list = [self.tab_widget.widget(i) for i in range(self.tab_widget.count())]
 
         # widget that are candidate not to be the owner of the kernel does have all the same port of the curent widget
         filtered_widget_list = ( widget for widget in widget_list if
                                 widget.kernel_client.connection_file == km.connection_file)
         # Get a list of all widget owning the same kernel and removed it from
         # the previous cadidate. (better using sets ?)
         master_widget_list = self.find_master_tab(tab, as_list=True)
         slave_list = [widget for widget in filtered_widget_list if widget not in master_widget_list]
 
         return slave_list
 
     # Populate the menu bar with common actions and shortcuts
     def add_menu_action(self, menu, action, defer_shortcut=False):
         """Add action to menu as well as self
         
         So that when the menu bar is invisible, its actions are still available.
         
         If defer_shortcut is True, set the shortcut context to widget-only,
         where it will avoid conflict with shortcuts already bound to the
         widgets themselves.
         """
         menu.addAction(action)
         self.addAction(action)
 
         if defer_shortcut:
             action.setShortcutContext(QtCore.Qt.WidgetShortcut)
     
     def init_menu_bar(self):
         #create menu in the order they should appear in the menu bar
         self.init_file_menu()
         self.init_edit_menu()
         self.init_view_menu()
         self.init_kernel_menu()
         self.init_magic_menu()
         self.init_window_menu()
         self.init_help_menu()
     
     def init_file_menu(self):
         self.file_menu = self.menuBar().addMenu("&File")
         
         self.new_kernel_tab_act = QtGui.QAction("New Tab with &New kernel",
             self,
             shortcut="Ctrl+T",
             triggered=self.create_tab_with_new_frontend)
         self.add_menu_action(self.file_menu, self.new_kernel_tab_act)
 
         self.slave_kernel_tab_act = QtGui.QAction("New Tab with Sa&me kernel",
             self,
             shortcut="Ctrl+Shift+T",
             triggered=self.create_tab_with_current_kernel)
         self.add_menu_action(self.file_menu, self.slave_kernel_tab_act)
         
         self.file_menu.addSeparator()
 
         self.close_action=QtGui.QAction("&Close Tab",
             self,
             shortcut=QtGui.QKeySequence.Close,
             triggered=self.close_active_frontend
             )
         self.add_menu_action(self.file_menu, self.close_action)
 
         self.export_action=QtGui.QAction("&Save to HTML/XHTML",
             self,
             shortcut=QtGui.QKeySequence.Save,
             triggered=self.export_action_active_frontend
             )
         self.add_menu_action(self.file_menu, self.export_action, True)
 
         self.file_menu.addSeparator()
         
         printkey = QtGui.QKeySequence(QtGui.QKeySequence.Print)
         if printkey.matches("Ctrl+P") and sys.platform != 'darwin':
             # Only override the default if there is a collision.
             # Qt ctrl = cmd on OSX, so the match gets a false positive on OSX.
             printkey = "Ctrl+Shift+P"
         self.print_action = QtGui.QAction("&Print",
             self,
             shortcut=printkey,
             triggered=self.print_action_active_frontend)
         self.add_menu_action(self.file_menu, self.print_action, True)
         
         if sys.platform != 'darwin':
             # OSX always has Quit in the Application menu, only add it
             # to the File menu elsewhere.
 
             self.file_menu.addSeparator()
 
             self.quit_action = QtGui.QAction("&Quit",
                 self,
                 shortcut=QtGui.QKeySequence.Quit,
                 triggered=self.close,
             )
             self.add_menu_action(self.file_menu, self.quit_action)
 
     
     def init_edit_menu(self):
         self.edit_menu = self.menuBar().addMenu("&Edit")
         
         self.undo_action = QtGui.QAction("&Undo",
             self,
             shortcut=QtGui.QKeySequence.Undo,
             statusTip="Undo last action if possible",
             triggered=self.undo_active_frontend
             )
         self.add_menu_action(self.edit_menu, self.undo_action)
 
         self.redo_action = QtGui.QAction("&Redo",
             self,
             shortcut=QtGui.QKeySequence.Redo,
             statusTip="Redo last action if possible",
             triggered=self.redo_active_frontend)
         self.add_menu_action(self.edit_menu, self.redo_action)
 
         self.edit_menu.addSeparator()
 
         self.cut_action = QtGui.QAction("&Cut",
             self,
             shortcut=QtGui.QKeySequence.Cut,
             triggered=self.cut_active_frontend
             )
         self.add_menu_action(self.edit_menu, self.cut_action, True)
 
         self.copy_action = QtGui.QAction("&Copy",
             self,
             shortcut=QtGui.QKeySequence.Copy,
             triggered=self.copy_active_frontend
             )
         self.add_menu_action(self.edit_menu, self.copy_action, True)
 
         self.copy_raw_action = QtGui.QAction("Copy (&Raw Text)",
             self,
             shortcut="Ctrl+Shift+C",
             triggered=self.copy_raw_active_frontend
             )
         self.add_menu_action(self.edit_menu, self.copy_raw_action, True)
 
         self.paste_action = QtGui.QAction("&Paste",
             self,
             shortcut=QtGui.QKeySequence.Paste,
             triggered=self.paste_active_frontend
             )
         self.add_menu_action(self.edit_menu, self.paste_action, True)
 
         self.edit_menu.addSeparator()
         
         selectall = QtGui.QKeySequence(QtGui.QKeySequence.SelectAll)
         if selectall.matches("Ctrl+A") and sys.platform != 'darwin':
             # Only override the default if there is a collision.
             # Qt ctrl = cmd on OSX, so the match gets a false positive on OSX.
             selectall = "Ctrl+Shift+A"
         self.select_all_action = QtGui.QAction("Select &All",
             self,
             shortcut=selectall,
             triggered=self.select_all_active_frontend
             )
         self.add_menu_action(self.edit_menu, self.select_all_action, True)
 
     
     def init_view_menu(self):
         self.view_menu = self.menuBar().addMenu("&View")
 
         if sys.platform != 'darwin':
             # disable on OSX, where there is always a menu bar
             self.toggle_menu_bar_act = QtGui.QAction("Toggle &Menu Bar",
                 self,
                 shortcut="Ctrl+Shift+M",
                 statusTip="Toggle visibility of menubar",
                 triggered=self.toggle_menu_bar)
             self.add_menu_action(self.view_menu, self.toggle_menu_bar_act)
         
         fs_key = "Ctrl+Meta+F" if sys.platform == 'darwin' else "F11"
         self.full_screen_act = QtGui.QAction("&Full Screen",
             self,
             shortcut=fs_key,
             statusTip="Toggle between Fullscreen and Normal Size",
             triggered=self.toggleFullScreen)
         self.add_menu_action(self.view_menu, self.full_screen_act)
 
         self.view_menu.addSeparator()
 
         self.increase_font_size = QtGui.QAction("Zoom &In",
             self,
             shortcut=QtGui.QKeySequence.ZoomIn,
             triggered=self.increase_font_size_active_frontend
             )
         self.add_menu_action(self.view_menu, self.increase_font_size, True)
 
         self.decrease_font_size = QtGui.QAction("Zoom &Out",
             self,
             shortcut=QtGui.QKeySequence.ZoomOut,
             triggered=self.decrease_font_size_active_frontend
             )
         self.add_menu_action(self.view_menu, self.decrease_font_size, True)
 
         self.reset_font_size = QtGui.QAction("Zoom &Reset",
             self,
             shortcut="Ctrl+0",
             triggered=self.reset_font_size_active_frontend
             )
         self.add_menu_action(self.view_menu, self.reset_font_size, True)
 
         self.view_menu.addSeparator()
 
         self.clear_action = QtGui.QAction("&Clear Screen",
             self,
             shortcut='Ctrl+L',
             statusTip="Clear the console",
             triggered=self.clear_magic_active_frontend)
         self.add_menu_action(self.view_menu, self.clear_action)
 
         self.pager_menu = self.view_menu.addMenu("&Pager")
 
         hsplit_action = QtGui.QAction(".. &Horizontal Split",
             self,
             triggered=lambda: self.set_paging_active_frontend('hsplit'))
 
         vsplit_action = QtGui.QAction(" : &Vertical Split",
             self,
             triggered=lambda: self.set_paging_active_frontend('vsplit'))
 
         inside_action = QtGui.QAction("   &Inside Pager",
             self,
             triggered=lambda: self.set_paging_active_frontend('inside'))
 
         self.pager_menu.addAction(hsplit_action)
         self.pager_menu.addAction(vsplit_action)
         self.pager_menu.addAction(inside_action)
 
     def init_kernel_menu(self):
         self.kernel_menu = self.menuBar().addMenu("&Kernel")
         # Qt on OSX maps Ctrl to Cmd, and Meta to Ctrl
         # keep the signal shortcuts to ctrl, rather than 
         # platform-default like we do elsewhere.
 
         ctrl = "Meta" if sys.platform == 'darwin' else "Ctrl"
 
         self.interrupt_kernel_action = QtGui.QAction("&Interrupt current Kernel",
             self,
             triggered=self.interrupt_kernel_active_frontend,
             shortcut=ctrl+"+C",
             )
         self.add_menu_action(self.kernel_menu, self.interrupt_kernel_action)
 
         self.restart_kernel_action = QtGui.QAction("&Restart current Kernel",
             self,
             triggered=self.restart_kernel_active_frontend,
             shortcut=ctrl+"+.",
             )
         self.add_menu_action(self.kernel_menu, self.restart_kernel_action)
 
         self.kernel_menu.addSeparator()
 
         self.confirm_restart_kernel_action = QtGui.QAction("&Confirm kernel restart",
             self,
             checkable=True,
             checked=self.active_frontend.confirm_restart,
             triggered=self.toggle_confirm_restart_active_frontend
             )
 
         self.add_menu_action(self.kernel_menu, self.confirm_restart_kernel_action)
         self.tab_widget.currentChanged.connect(self.update_restart_checkbox)
         
     def init_magic_menu(self):
         self.magic_menu = self.menuBar().addMenu("&Magic")
 
         self.add_menu_action(self.magic_menu, 
                              self.magic_helper.toggleViewAction())
 
         self.magic_menu_separator = self.magic_menu.addSeparator()
         
         self.reset_action = QtGui.QAction("&Reset",
             self,
             statusTip="Clear all variables from workspace",
             triggered=self.reset_magic_active_frontend)
         self.add_menu_action(self.magic_menu, self.reset_action)
 
         self.history_action = QtGui.QAction("&History",
             self,
             statusTip="show command history",
             triggered=self.history_magic_active_frontend)
         self.add_menu_action(self.magic_menu, self.history_action)
 
         self.save_action = QtGui.QAction("E&xport History ",
             self,
             statusTip="Export History as Python File",
             triggered=self.save_magic_active_frontend)
         self.add_menu_action(self.magic_menu, self.save_action)
 
         self.who_action = QtGui.QAction("&Who",
             self,
             statusTip="List interactive variables",
             triggered=self.who_magic_active_frontend)
         self.add_menu_action(self.magic_menu, self.who_action)
 
         self.who_ls_action = QtGui.QAction("Wh&o ls",
             self,
             statusTip="Return a list of interactive variables",
             triggered=self.who_ls_magic_active_frontend)
         self.add_menu_action(self.magic_menu, self.who_ls_action)
 
         self.whos_action = QtGui.QAction("Who&s",
             self,
             statusTip="List interactive variables with details",
             triggered=self.whos_magic_active_frontend)
         self.add_menu_action(self.magic_menu, self.whos_action)
 
     def init_window_menu(self):
         self.window_menu = self.menuBar().addMenu("&Window")
         if sys.platform == 'darwin':
             # add min/maximize actions to OSX, which lacks default bindings.
             self.minimizeAct = QtGui.QAction("Mini&mize",
                 self,
                 shortcut="Ctrl+m",
                 statusTip="Minimize the window/Restore Normal Size",
                 triggered=self.toggleMinimized)
             # maximize is called 'Zoom' on OSX for some reason
             self.maximizeAct = QtGui.QAction("&Zoom",
                 self,
                 shortcut="Ctrl+Shift+M",
                 statusTip="Maximize the window/Restore Normal Size",
                 triggered=self.toggleMaximized)
 
             self.add_menu_action(self.window_menu, self.minimizeAct)
             self.add_menu_action(self.window_menu, self.maximizeAct)
             self.window_menu.addSeparator()
 
         prev_key = "Ctrl+Shift+Left" if sys.platform == 'darwin' else "Ctrl+PgUp"
         self.prev_tab_act = QtGui.QAction("Pre&vious Tab",
             self,
             shortcut=prev_key,
             statusTip="Select previous tab",
             triggered=self.prev_tab)
         self.add_menu_action(self.window_menu, self.prev_tab_act)
 
         next_key = "Ctrl+Shift+Right" if sys.platform == 'darwin' else "Ctrl+PgDown"
         self.next_tab_act = QtGui.QAction("Ne&xt Tab",
             self,
             shortcut=next_key,
             statusTip="Select next tab",
             triggered=self.next_tab)
         self.add_menu_action(self.window_menu, self.next_tab_act)
     
     def init_help_menu(self):
         # please keep the Help menu in Mac Os even if empty. It will
         # automatically contain a search field to search inside menus and
         # please keep it spelled in English, as long as Qt Doesn't support
         # a QAction.MenuRole like HelpMenuRole otherwise it will lose
         # this search field functionality
 
         self.help_menu = self.menuBar().addMenu("&Help")
         
 
         # Help Menu
 
         self.intro_active_frontend_action = QtGui.QAction("&Intro to IPython",
             self,
             triggered=self.intro_active_frontend
             )
         self.add_menu_action(self.help_menu, self.intro_active_frontend_action)
 
         self.quickref_active_frontend_action = QtGui.QAction("IPython &Cheat Sheet",
             self,
             triggered=self.quickref_active_frontend
             )
         self.add_menu_action(self.help_menu, self.quickref_active_frontend_action)
 
         self.guiref_active_frontend_action = QtGui.QAction("&Qt Console",
             self,
             triggered=self.guiref_active_frontend
             )
         self.add_menu_action(self.help_menu, self.guiref_active_frontend_action)
 
         self.onlineHelpAct = QtGui.QAction("Open Online &Help",
             self,
             triggered=self._open_online_help)
         self.add_menu_action(self.help_menu, self.onlineHelpAct)
 
     def init_magic_helper(self):
         from .magic_helper import MagicHelper
 
         self.magic_helper = MagicHelper("Show Magics", self)
 
         self.magic_helper.setAllowedAreas(QtCore.Qt.LeftDockWidgetArea | 
                                           QtCore.Qt.RightDockWidgetArea)        
         self.magic_helper.setVisible(False)
 
         self.magic_helper.pasteRequested[str].connect(
             self.magic_helper_paste_requested
         )
         self.magic_helper.runRequested[str].connect(
             self.magic_helper_run_requested
         )
         self.magic_helper.readyForUpdate.connect(
             self.magic_helper_update_requested
         )
 
         self.addDockWidget(QtCore.Qt.RightDockWidgetArea, self.magic_helper)
 
     def _set_active_frontend_focus(self):
         # this is a hack, self.active_frontend._control seems to be 
         # a private member. Unfortunately this is the only method 
         # to set focus reliably
         QtCore.QTimer.singleShot(200, self.active_frontend._control.setFocus)
 
     def magic_helper_paste_requested(self, text = None):
-        if text != None:
+        if text is not None:
             self.active_frontend.input_buffer = text            
             self._set_active_frontend_focus()
 
     def magic_helper_run_requested(self, text = None):
-        if text != None:            
+        if text is not None:
             self.active_frontend.execute(text)  
             self._set_active_frontend_focus()
 
     def magic_helper_update_requested(self):
         def _handle_data(data):
             if not data:
                 return
 
             if data['status'] != 'ok':
                 self.log.warn( 
                     "%%lsmagic user-expression failed: {}".format(data)
                 )
                 return
             self.magic_helper.populate_magic_helper(data)
 
         self.active_frontend._silent_exec_callback(
             'get_ipython().magic("lsmagic")',
             _handle_data
         )
 
     # minimize/maximize/fullscreen actions:
 
     def toggle_menu_bar(self):
         menu_bar = self.menuBar()
         if menu_bar.isVisible():
             menu_bar.setVisible(False)
         else:
             menu_bar.setVisible(True)
 
     def toggleMinimized(self):
         if not self.isMinimized():
             self.showMinimized()
         else:
             self.showNormal()
 
     def _open_online_help(self):
         filename="http://ipython.org/ipython-doc/stable/index.html"
         webbrowser.open(filename, new=1, autoraise=True)
 
     def toggleMaximized(self):
         if not self.isMaximized():
             self.showMaximized()
         else:
             self.showNormal()
 
     # Min/Max imizing while in full screen give a bug
     # when going out of full screen, at least on OSX
     def toggleFullScreen(self):
         if not self.isFullScreen():
             self.showFullScreen()
             if sys.platform == 'darwin':
                 self.maximizeAct.setEnabled(False)
                 self.minimizeAct.setEnabled(False)
         else:
             self.showNormal()
             if sys.platform == 'darwin':
                 self.maximizeAct.setEnabled(True)
                 self.minimizeAct.setEnabled(True)
 
     def set_paging_active_frontend(self, paging):
         self.active_frontend._set_paging(paging)
 
     def close_active_frontend(self):
         self.close_tab(self.active_frontend)
 
     def restart_kernel_active_frontend(self):
         self.active_frontend.request_restart_kernel()
 
     def interrupt_kernel_active_frontend(self):
         self.active_frontend.request_interrupt_kernel()
 
     def toggle_confirm_restart_active_frontend(self):
         widget = self.active_frontend
         widget.confirm_restart = not widget.confirm_restart
         self.confirm_restart_kernel_action.setChecked(widget.confirm_restart)
 
     def update_restart_checkbox(self):
         if self.active_frontend is None:
             return
         widget = self.active_frontend
         self.confirm_restart_kernel_action.setChecked(widget.confirm_restart)
 
     def cut_active_frontend(self):
         widget = self.active_frontend
         if widget.can_cut():
             widget.cut()
 
     def copy_active_frontend(self):
         widget = self.active_frontend
         widget.copy()
 
     def copy_raw_active_frontend(self):
         self.active_frontend._copy_raw_action.trigger()
 
     def paste_active_frontend(self):
         widget = self.active_frontend
         if widget.can_paste():
             widget.paste()
 
     def undo_active_frontend(self):
         self.active_frontend.undo()
 
     def redo_active_frontend(self):
         self.active_frontend.redo()
 
     def reset_magic_active_frontend(self):
         self.active_frontend.execute("%reset")
 
     def history_magic_active_frontend(self):
         self.active_frontend.execute("%history")
 
     def save_magic_active_frontend(self):
         self.active_frontend.save_magic()
 
     def clear_magic_active_frontend(self):
         self.active_frontend.execute("%clear")
 
     def who_magic_active_frontend(self):
         self.active_frontend.execute("%who")
 
     def who_ls_magic_active_frontend(self):
         self.active_frontend.execute("%who_ls")
 
     def whos_magic_active_frontend(self):
         self.active_frontend.execute("%whos")
 
     def print_action_active_frontend(self):
         self.active_frontend.print_action.trigger()
 
     def export_action_active_frontend(self):
         self.active_frontend.export_action.trigger()
 
     def select_all_active_frontend(self):
         self.active_frontend.select_all_action.trigger()
 
     def increase_font_size_active_frontend(self):
         self.active_frontend.increase_font_size.trigger()
 
     def decrease_font_size_active_frontend(self):
         self.active_frontend.decrease_font_size.trigger()
 
     def reset_font_size_active_frontend(self):
         self.active_frontend.reset_font_size.trigger()
 
     def guiref_active_frontend(self):
         self.active_frontend.execute("%guiref")
 
     def intro_active_frontend(self):
         self.active_frontend.execute("?")
 
     def quickref_active_frontend(self):
         self.active_frontend.execute("%quickref")
     #---------------------------------------------------------------------------
     # QWidget interface
     #---------------------------------------------------------------------------
 
     def closeEvent(self, event):
         """ Forward the close event to every tabs contained by the windows
         """
         if self.tab_widget.count() == 0:
             # no tabs, just close
             event.accept()
             return
         # Do Not loop on the widget count as it change while closing
         title = self.window().windowTitle()
         cancel = QtGui.QMessageBox.Cancel
         okay = QtGui.QMessageBox.Ok
         accept_role = QtGui.QMessageBox.AcceptRole
         
         if self.confirm_exit:
             if self.tab_widget.count() > 1:
                 msg = "Close all tabs, stop all kernels, and Quit?"
             else:
                 msg = "Close console, stop kernel, and Quit?"
             info = "Kernels not started here (e.g. notebooks) will be left alone."
             closeall = QtGui.QPushButton("&Quit", self)
             closeall.setShortcut('Q')
             box = QtGui.QMessageBox(QtGui.QMessageBox.Question,
                                     title, msg)
             box.setInformativeText(info)
             box.addButton(cancel)
             box.addButton(closeall, QtGui.QMessageBox.YesRole)
             box.setDefaultButton(closeall)
             box.setEscapeButton(cancel)
             pixmap = QtGui.QPixmap(self._app.icon.pixmap(QtCore.QSize(64,64)))
             box.setIconPixmap(pixmap)
             reply = box.exec_()
         else:
             reply = okay
         
         if reply == cancel:
             event.ignore()
             return
         if reply == okay or reply == accept_role:
             while self.tab_widget.count() >= 1:
                 # prevent further confirmations:
                 widget = self.active_frontend
                 widget._confirm_exit = False
                 self.close_tab(widget)
             event.accept()
 

IPython/utils/_process_win32_controller.py

@@ -1,577 +1,577 b''
 """Windows-specific implementation of process utilities with direct WinAPI.
 
 This file is meant to be used by process.py
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2010-2011  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 
 from __future__ import print_function
 
 # stdlib
 import os, sys, threading
 import ctypes, msvcrt
 
 # local imports
 from . import py3compat
 
 # Win32 API types needed for the API calls
 from ctypes import POINTER
 from ctypes.wintypes import HANDLE, HLOCAL, LPVOID, WORD, DWORD, BOOL, \
         ULONG, LPCWSTR
 LPDWORD = POINTER(DWORD)
 LPHANDLE = POINTER(HANDLE)
 ULONG_PTR = POINTER(ULONG)
 class SECURITY_ATTRIBUTES(ctypes.Structure):
     _fields_ = [("nLength", DWORD),
                 ("lpSecurityDescriptor", LPVOID),
                 ("bInheritHandle", BOOL)]
 LPSECURITY_ATTRIBUTES = POINTER(SECURITY_ATTRIBUTES)
 class STARTUPINFO(ctypes.Structure):
     _fields_ = [("cb", DWORD),
                 ("lpReserved", LPCWSTR),
                 ("lpDesktop", LPCWSTR),
                 ("lpTitle", LPCWSTR),
                 ("dwX", DWORD),
                 ("dwY", DWORD),
                 ("dwXSize", DWORD),
                 ("dwYSize", DWORD),
                 ("dwXCountChars", DWORD),
                 ("dwYCountChars", DWORD),
                 ("dwFillAttribute", DWORD),
                 ("dwFlags", DWORD),
                 ("wShowWindow", WORD),
                 ("cbReserved2", WORD),
                 ("lpReserved2", LPVOID),
                 ("hStdInput", HANDLE),
                 ("hStdOutput", HANDLE),
                 ("hStdError", HANDLE)]
 LPSTARTUPINFO = POINTER(STARTUPINFO)
 class PROCESS_INFORMATION(ctypes.Structure):
     _fields_ = [("hProcess", HANDLE),
                 ("hThread", HANDLE),
                 ("dwProcessId", DWORD),
                 ("dwThreadId", DWORD)]
 LPPROCESS_INFORMATION = POINTER(PROCESS_INFORMATION)
 
 # Win32 API constants needed
 ERROR_HANDLE_EOF = 38
 ERROR_BROKEN_PIPE = 109
 ERROR_NO_DATA = 232
 HANDLE_FLAG_INHERIT = 0x0001
 STARTF_USESTDHANDLES = 0x0100
 CREATE_SUSPENDED = 0x0004
 CREATE_NEW_CONSOLE = 0x0010
 CREATE_NO_WINDOW = 0x08000000
 STILL_ACTIVE = 259
 WAIT_TIMEOUT = 0x0102
 WAIT_FAILED = 0xFFFFFFFF
 INFINITE = 0xFFFFFFFF
 DUPLICATE_SAME_ACCESS = 0x00000002
 ENABLE_ECHO_INPUT = 0x0004
 ENABLE_LINE_INPUT = 0x0002
 ENABLE_PROCESSED_INPUT = 0x0001
 
 # Win32 API functions needed
 GetLastError = ctypes.windll.kernel32.GetLastError
 GetLastError.argtypes = []
 GetLastError.restype = DWORD
 
 CreateFile = ctypes.windll.kernel32.CreateFileW
 CreateFile.argtypes = [LPCWSTR, DWORD, DWORD, LPVOID, DWORD, DWORD, HANDLE]
 CreateFile.restype = HANDLE
 
 CreatePipe = ctypes.windll.kernel32.CreatePipe
 CreatePipe.argtypes = [POINTER(HANDLE), POINTER(HANDLE),
         LPSECURITY_ATTRIBUTES, DWORD]
 CreatePipe.restype = BOOL
 
 CreateProcess = ctypes.windll.kernel32.CreateProcessW
 CreateProcess.argtypes = [LPCWSTR, LPCWSTR, LPSECURITY_ATTRIBUTES,
         LPSECURITY_ATTRIBUTES, BOOL, DWORD, LPVOID, LPCWSTR, LPSTARTUPINFO,
         LPPROCESS_INFORMATION]
 CreateProcess.restype = BOOL
 
 GetExitCodeProcess = ctypes.windll.kernel32.GetExitCodeProcess
 GetExitCodeProcess.argtypes = [HANDLE, LPDWORD]
 GetExitCodeProcess.restype = BOOL
 
 GetCurrentProcess = ctypes.windll.kernel32.GetCurrentProcess
 GetCurrentProcess.argtypes = []
 GetCurrentProcess.restype = HANDLE
 
 ResumeThread = ctypes.windll.kernel32.ResumeThread
 ResumeThread.argtypes = [HANDLE]
 ResumeThread.restype = DWORD
 
 ReadFile = ctypes.windll.kernel32.ReadFile
 ReadFile.argtypes = [HANDLE, LPVOID, DWORD, LPDWORD, LPVOID]
 ReadFile.restype = BOOL
 
 WriteFile = ctypes.windll.kernel32.WriteFile
 WriteFile.argtypes = [HANDLE, LPVOID, DWORD, LPDWORD, LPVOID]
 WriteFile.restype = BOOL
 
 GetConsoleMode = ctypes.windll.kernel32.GetConsoleMode
 GetConsoleMode.argtypes = [HANDLE, LPDWORD]
 GetConsoleMode.restype = BOOL
 
 SetConsoleMode = ctypes.windll.kernel32.SetConsoleMode
 SetConsoleMode.argtypes = [HANDLE, DWORD]
 SetConsoleMode.restype = BOOL
 
 FlushConsoleInputBuffer = ctypes.windll.kernel32.FlushConsoleInputBuffer
 FlushConsoleInputBuffer.argtypes = [HANDLE]
 FlushConsoleInputBuffer.restype = BOOL
 
 WaitForSingleObject = ctypes.windll.kernel32.WaitForSingleObject
 WaitForSingleObject.argtypes = [HANDLE, DWORD]
 WaitForSingleObject.restype = DWORD
 
 DuplicateHandle = ctypes.windll.kernel32.DuplicateHandle
 DuplicateHandle.argtypes = [HANDLE, HANDLE, HANDLE, LPHANDLE,
         DWORD, BOOL, DWORD]
 DuplicateHandle.restype = BOOL
 
 SetHandleInformation = ctypes.windll.kernel32.SetHandleInformation
 SetHandleInformation.argtypes = [HANDLE, DWORD, DWORD]
 SetHandleInformation.restype = BOOL
 
 CloseHandle = ctypes.windll.kernel32.CloseHandle
 CloseHandle.argtypes = [HANDLE]
 CloseHandle.restype = BOOL
 
 CommandLineToArgvW = ctypes.windll.shell32.CommandLineToArgvW
 CommandLineToArgvW.argtypes = [LPCWSTR, POINTER(ctypes.c_int)]
 CommandLineToArgvW.restype = POINTER(LPCWSTR)
 
 LocalFree = ctypes.windll.kernel32.LocalFree
 LocalFree.argtypes = [HLOCAL]
 LocalFree.restype = HLOCAL
 
 class AvoidUNCPath(object):
     """A context manager to protect command execution from UNC paths.
 
     In the Win32 API, commands can't be invoked with the cwd being a UNC path.
     This context manager temporarily changes directory to the 'C:' drive on
     entering, and restores the original working directory on exit.
 
     The context manager returns the starting working directory *if* it made a
     change and None otherwise, so that users can apply the necessary adjustment
     to their system calls in the event of a change.
 
     Examples
     --------
     ::
         cmd = 'dir'
         with AvoidUNCPath() as path:
             if path is not None:
                 cmd = '"pushd %s &&"%s' % (path, cmd)
             os.system(cmd)
     """
     def __enter__(self):
         self.path = py3compat.getcwd()
         self.is_unc_path = self.path.startswith(r"\\")
         if self.is_unc_path:
             # change to c drive (as cmd.exe cannot handle UNC addresses)
             os.chdir("C:")
             return self.path
         else:
             # We return None to signal that there was no change in the working
             # directory
             return None
 
     def __exit__(self, exc_type, exc_value, traceback):
         if self.is_unc_path:
             os.chdir(self.path)
 
 
 class Win32ShellCommandController(object):
     """Runs a shell command in a 'with' context.
 
     This implementation is Win32-specific.
 
     Example:
         # Runs the command interactively with default console stdin/stdout
         with ShellCommandController('python -i') as scc:
             scc.run()
 
         # Runs the command using the provided functions for stdin/stdout
         def my_stdout_func(s):
             # print or save the string 's'
             write_to_stdout(s)
         def my_stdin_func():
             # If input is available, return it as a string.
             if input_available():
                 return get_input()
             # If no input available, return None after a short delay to
             # keep from blocking.
             else:
                 time.sleep(0.01)
                 return None
       
         with ShellCommandController('python -i') as scc:
             scc.run(my_stdout_func, my_stdin_func)
     """
 
     def __init__(self, cmd, mergeout = True):
         """Initializes the shell command controller.
 
         The cmd is the program to execute, and mergeout is
         whether to blend stdout and stderr into one output
         in stdout. Merging them together in this fashion more
         reliably keeps stdout and stderr in the correct order
         especially for interactive shell usage.
         """
         self.cmd = cmd
         self.mergeout = mergeout
 
     def __enter__(self):
         cmd = self.cmd
         mergeout = self.mergeout
 
         self.hstdout, self.hstdin, self.hstderr = None, None, None
         self.piProcInfo = None
         try:
             p_hstdout, c_hstdout, p_hstderr, \
                     c_hstderr, p_hstdin, c_hstdin = [None]*6
 
             # SECURITY_ATTRIBUTES with inherit handle set to True
             saAttr = SECURITY_ATTRIBUTES()
             saAttr.nLength = ctypes.sizeof(saAttr)
             saAttr.bInheritHandle = True
             saAttr.lpSecurityDescriptor = None
 
             def create_pipe(uninherit):
                 """Creates a Windows pipe, which consists of two handles.
 
                 The 'uninherit' parameter controls which handle is not
                 inherited by the child process.
                 """
                 handles = HANDLE(), HANDLE()
                 if not CreatePipe(ctypes.byref(handles[0]),
                             ctypes.byref(handles[1]), ctypes.byref(saAttr), 0):
                     raise ctypes.WinError()
                 if not SetHandleInformation(handles[uninherit],
                             HANDLE_FLAG_INHERIT, 0):
                     raise ctypes.WinError()
                 return handles[0].value, handles[1].value
 
             p_hstdout, c_hstdout = create_pipe(uninherit=0)
             # 'mergeout' signals that stdout and stderr should be merged.
             # We do that by using one pipe for both of them.
             if mergeout:
                 c_hstderr = HANDLE()
                 if not DuplicateHandle(GetCurrentProcess(), c_hstdout,
                                 GetCurrentProcess(), ctypes.byref(c_hstderr),
                                 0, True, DUPLICATE_SAME_ACCESS):
                     raise ctypes.WinError()
             else:
                 p_hstderr, c_hstderr = create_pipe(uninherit=0)
             c_hstdin,  p_hstdin  = create_pipe(uninherit=1)
 
             # Create the process object
             piProcInfo = PROCESS_INFORMATION()
             siStartInfo = STARTUPINFO()
             siStartInfo.cb = ctypes.sizeof(siStartInfo)
             siStartInfo.hStdInput = c_hstdin
             siStartInfo.hStdOutput = c_hstdout
             siStartInfo.hStdError = c_hstderr
             siStartInfo.dwFlags = STARTF_USESTDHANDLES
             dwCreationFlags = CREATE_SUSPENDED | CREATE_NO_WINDOW # | CREATE_NEW_CONSOLE
 
             if not CreateProcess(None,
                     u"cmd.exe /c " + cmd,
                     None, None, True, dwCreationFlags,
                     None, None, ctypes.byref(siStartInfo),
                     ctypes.byref(piProcInfo)):
                 raise ctypes.WinError()
 
             # Close this process's versions of the child handles
             CloseHandle(c_hstdin)
             c_hstdin = None
             CloseHandle(c_hstdout)
             c_hstdout = None
-            if c_hstderr != None:
+            if c_hstderr is not None:
                 CloseHandle(c_hstderr)
                 c_hstderr = None
 
             # Transfer ownership of the parent handles to the object
             self.hstdin = p_hstdin
             p_hstdin = None
             self.hstdout = p_hstdout
             p_hstdout = None
             if not mergeout:
                 self.hstderr = p_hstderr
                 p_hstderr = None
             self.piProcInfo = piProcInfo
 
         finally:
             if p_hstdin:
                 CloseHandle(p_hstdin)
             if c_hstdin:
                 CloseHandle(c_hstdin)
             if p_hstdout:
                 CloseHandle(p_hstdout)
             if c_hstdout:
                 CloseHandle(c_hstdout)
             if p_hstderr:
                 CloseHandle(p_hstderr)
             if c_hstderr:
                 CloseHandle(c_hstderr)
 
         return self
 
     def _stdin_thread(self, handle, hprocess, func, stdout_func):
         exitCode = DWORD()
         bytesWritten = DWORD(0)
         while True:
             #print("stdin thread loop start")
             # Get the input string (may be bytes or unicode)
             data = func()
 
             # None signals to poll whether the process has exited
             if data is None:
                 #print("checking for process completion")
                 if not GetExitCodeProcess(hprocess, ctypes.byref(exitCode)):
                     raise ctypes.WinError()
                 if exitCode.value != STILL_ACTIVE:
                     return
                 # TESTING: Does zero-sized writefile help?
                 if not WriteFile(handle, "", 0,
                         ctypes.byref(bytesWritten), None):
                     raise ctypes.WinError()
                 continue
             #print("\nGot str %s\n" % repr(data), file=sys.stderr)
 
             # Encode the string to the console encoding
             if isinstance(data, unicode): #FIXME: Python3
                 data = data.encode('utf_8')
 
             # What we have now must be a string of bytes
             if not isinstance(data, str): #FIXME: Python3
                 raise RuntimeError("internal stdin function string error")
 
             # An empty string signals EOF
             if len(data) == 0:
                 return
 
             # In a windows console, sometimes the input is echoed,
             # but sometimes not. How do we determine when to do this?
             stdout_func(data)
             # WriteFile may not accept all the data at once.
             # Loop until everything is processed
             while len(data) != 0:
                 #print("Calling writefile")
                 if not WriteFile(handle, data, len(data),
                         ctypes.byref(bytesWritten), None):
                     # This occurs at exit
                     if GetLastError() == ERROR_NO_DATA:
                         return
                     raise ctypes.WinError()
                 #print("Called writefile")
                 data = data[bytesWritten.value:]
 
     def _stdout_thread(self, handle, func):
         # Allocate the output buffer
         data = ctypes.create_string_buffer(4096)
         while True:
             bytesRead = DWORD(0)
             if not ReadFile(handle, data, 4096,
                         ctypes.byref(bytesRead), None):
                 le = GetLastError()
                 if le == ERROR_BROKEN_PIPE:
                     return
                 else:
                     raise ctypes.WinError()
             # FIXME: Python3
             s = data.value[0:bytesRead.value]
             #print("\nv: %s" % repr(s), file=sys.stderr)
             func(s.decode('utf_8', 'replace'))
 
     def run(self, stdout_func = None, stdin_func = None, stderr_func = None):
         """Runs the process, using the provided functions for I/O.
 
         The function stdin_func should return strings whenever a
         character or characters become available.
         The functions stdout_func and stderr_func are called whenever
         something is printed to stdout or stderr, respectively.
         These functions are called from different threads (but not
         concurrently, because of the GIL).
         """
-        if stdout_func == None and stdin_func == None and stderr_func == None:
+        if stdout_func is None and stdin_func is None and stderr_func is None:
             return self._run_stdio()
 
-        if stderr_func != None and self.mergeout:
+        if stderr_func is not None and self.mergeout:
             raise RuntimeError("Shell command was initiated with "
                     "merged stdin/stdout, but a separate stderr_func "
                     "was provided to the run() method")
 
         # Create a thread for each input/output handle
         stdin_thread = None
         threads = []
         if stdin_func:
             stdin_thread = threading.Thread(target=self._stdin_thread,
                                 args=(self.hstdin, self.piProcInfo.hProcess,
                                 stdin_func, stdout_func))
         threads.append(threading.Thread(target=self._stdout_thread,
                                     args=(self.hstdout, stdout_func)))
         if not self.mergeout:
-            if stderr_func == None:
+            if stderr_func is None:
                 stderr_func = stdout_func
             threads.append(threading.Thread(target=self._stdout_thread,
                                         args=(self.hstderr, stderr_func)))
         # Start the I/O threads and the process
         if ResumeThread(self.piProcInfo.hThread) == 0xFFFFFFFF:
             raise ctypes.WinError()
         if stdin_thread is not None:
             stdin_thread.start()
         for thread in threads:
             thread.start()
         # Wait for the process to complete
         if WaitForSingleObject(self.piProcInfo.hProcess, INFINITE) == \
                     WAIT_FAILED:
             raise ctypes.WinError()
         # Wait for the I/O threads to complete
         for thread in threads:
             thread.join()
 
         # Wait for the stdin thread to complete
         if stdin_thread is not None:
             stdin_thread.join()
 
     def _stdin_raw_nonblock(self):
         """Use the raw Win32 handle of sys.stdin to do non-blocking reads"""
         # WARNING: This is experimental, and produces inconsistent results.
         #          It's possible for the handle not to be appropriate for use
         #          with WaitForSingleObject, among other things.
         handle = msvcrt.get_osfhandle(sys.stdin.fileno())
         result = WaitForSingleObject(handle, 100)
         if result == WAIT_FAILED:
             raise ctypes.WinError()
         elif result == WAIT_TIMEOUT:
             print(".", end='')
             return None
         else:
             data = ctypes.create_string_buffer(256)
             bytesRead = DWORD(0)
             print('?', end='')
 
             if not ReadFile(handle, data, 256,
                         ctypes.byref(bytesRead), None):
                 raise ctypes.WinError()
             # This ensures the non-blocking works with an actual console
             # Not checking the error, so the processing will still work with
             # other handle types
             FlushConsoleInputBuffer(handle)
 
             data = data.value
             data = data.replace('\r\n', '\n')
             data = data.replace('\r', '\n')
             print(repr(data) + " ", end='')
             return data
 
     def _stdin_raw_block(self):
         """Use a blocking stdin read"""
         # The big problem with the blocking read is that it doesn't
         # exit when it's supposed to in all contexts. An extra
         # key-press may be required to trigger the exit.
         try:
             data = sys.stdin.read(1)
             data = data.replace('\r', '\n')
             return data
         except WindowsError as we:
             if we.winerror == ERROR_NO_DATA:
                 # This error occurs when the pipe is closed
                 return None
             else:
                 # Otherwise let the error propagate
                 raise we
 
     def _stdout_raw(self, s):
         """Writes the string to stdout"""
         print(s, end='', file=sys.stdout)
         sys.stdout.flush()
 
     def _stderr_raw(self, s):
         """Writes the string to stdout"""
         print(s, end='', file=sys.stderr)
         sys.stderr.flush()
 
     def _run_stdio(self):
         """Runs the process using the system standard I/O.
 
         IMPORTANT: stdin needs to be asynchronous, so the Python
                    sys.stdin object is not used. Instead,
                    msvcrt.kbhit/getwch are used asynchronously.
         """
         # Disable Line and Echo mode
         #lpMode = DWORD()
         #handle = msvcrt.get_osfhandle(sys.stdin.fileno())
         #if GetConsoleMode(handle, ctypes.byref(lpMode)):
         #    set_console_mode = True
         #    if not SetConsoleMode(handle, lpMode.value &
         #            ~(ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT | ENABLE_PROCESSED_INPUT)):
         #        raise ctypes.WinError()
 
         if self.mergeout:
             return self.run(stdout_func = self._stdout_raw,
                     stdin_func = self._stdin_raw_block)
         else:
             return self.run(stdout_func = self._stdout_raw,
                     stdin_func = self._stdin_raw_block,
                     stderr_func = self._stderr_raw)
 
         # Restore the previous console mode
         #if set_console_mode:
         #    if not SetConsoleMode(handle, lpMode.value):
         #        raise ctypes.WinError()
 
     def __exit__(self, exc_type, exc_value, traceback):
         if self.hstdin:
             CloseHandle(self.hstdin)
             self.hstdin = None
         if self.hstdout:
             CloseHandle(self.hstdout)
             self.hstdout = None
         if self.hstderr:
             CloseHandle(self.hstderr)
             self.hstderr = None
-        if self.piProcInfo != None:
+        if self.piProcInfo is not None:
             CloseHandle(self.piProcInfo.hProcess)
             CloseHandle(self.piProcInfo.hThread)
             self.piProcInfo = None
 
 
 def system(cmd):
     """Win32 version of os.system() that works with network shares.
 
     Note that this implementation returns None, as meant for use in IPython.
 
     Parameters
     ----------
     cmd : str
       A command to be executed in the system shell.
 
     Returns
     -------
     None : we explicitly do NOT return the subprocess status code, as this
     utility is meant to be used extensively in IPython, where any return value
     would trigger :func:`sys.displayhook` calls.
     """
     with AvoidUNCPath() as path:
         if path is not None:
             cmd = '"pushd %s &&"%s' % (path, cmd)
         with Win32ShellCommandController(cmd) as scc:
             scc.run()
 
 
 if __name__ == "__main__":
     print("Test starting!")
     #system("cmd")
     system("python -i")
     print("Test finished!")