Vehicle-Anti-Theft-Face-Rec.../venv/Lib/site-packages/qtconsole/frontend_widget.py

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2020-11-12 16:05:57 +00:00
"""Frontend widget for the Qt Console"""
# Copyright (c) Jupyter Development Team
# Distributed under the terms of the Modified BSD License.
from __future__ import print_function
from collections import namedtuple
import sys
import uuid
import re
from qtpy import QtCore, QtGui, QtWidgets
from ipython_genutils import py3compat
from ipython_genutils.importstring import import_item
from qtconsole.base_frontend_mixin import BaseFrontendMixin
from traitlets import Any, Bool, Instance, Unicode, DottedObjectName, default
from .bracket_matcher import BracketMatcher
from .call_tip_widget import CallTipWidget
from .history_console_widget import HistoryConsoleWidget
from .pygments_highlighter import PygmentsHighlighter
class FrontendHighlighter(PygmentsHighlighter):
""" A PygmentsHighlighter that understands and ignores prompts.
"""
def __init__(self, frontend, lexer=None):
super(FrontendHighlighter, self).__init__(frontend._control.document(), lexer=lexer)
self._current_offset = 0
self._frontend = frontend
self.highlighting_on = False
self._classic_prompt_re = re.compile(
r'^(%s)?([ \t]*>>> |^[ \t]*\.\.\. )' % re.escape(frontend.other_output_prefix)
)
self._ipy_prompt_re = re.compile(
r'^(%s)?([ \t]*In \[\d+\]: |[ \t]*\ \ \ \.\.\.+: )' % re.escape(frontend.other_output_prefix)
)
def transform_classic_prompt(self, line):
"""Handle inputs that start with '>>> ' syntax."""
if not line or line.isspace():
return line
m = self._classic_prompt_re.match(line)
if m:
return line[len(m.group(0)):]
else:
return line
def transform_ipy_prompt(self, line):
"""Handle inputs that start classic IPython prompt syntax."""
if not line or line.isspace():
return line
m = self._ipy_prompt_re.match(line)
if m:
return line[len(m.group(0)):]
else:
return line
def highlightBlock(self, string):
""" Highlight a block of text. Reimplemented to highlight selectively.
"""
if not hasattr(self, 'highlighting_on') or not self.highlighting_on:
return
# The input to this function is a unicode string that may contain
# paragraph break characters, non-breaking spaces, etc. Here we acquire
# the string as plain text so we can compare it.
current_block = self.currentBlock()
string = self._frontend._get_block_plain_text(current_block)
# Only highlight if we can identify a prompt, but make sure not to
# highlight the prompt.
without_prompt = self.transform_ipy_prompt(string)
diff = len(string) - len(without_prompt)
if diff > 0:
self._current_offset = diff
super(FrontendHighlighter, self).highlightBlock(without_prompt)
def rehighlightBlock(self, block):
""" Reimplemented to temporarily enable highlighting if disabled.
"""
old = self.highlighting_on
self.highlighting_on = True
super(FrontendHighlighter, self).rehighlightBlock(block)
self.highlighting_on = old
def setFormat(self, start, count, format):
""" Reimplemented to highlight selectively.
"""
start += self._current_offset
super(FrontendHighlighter, self).setFormat(start, count, format)
class FrontendWidget(HistoryConsoleWidget, BaseFrontendMixin):
""" A Qt frontend for a generic Python kernel.
"""
# The text to show when the kernel is (re)started.
banner = Unicode(config=True)
kernel_banner = Unicode()
# Whether to show the banner
_display_banner = Bool(False)
# An option and corresponding signal for overriding the default kernel
# interrupt behavior.
custom_interrupt = Bool(False)
custom_interrupt_requested = QtCore.Signal()
# An option and corresponding signals for overriding the default kernel
# restart behavior.
custom_restart = Bool(False)
custom_restart_kernel_died = QtCore.Signal(float)
custom_restart_requested = QtCore.Signal()
# Whether to automatically show calltips on open-parentheses.
enable_calltips = Bool(True, config=True,
help="Whether to draw information calltips on open-parentheses.")
clear_on_kernel_restart = Bool(True, config=True,
help="Whether to clear the console when the kernel is restarted")
confirm_restart = Bool(True, config=True,
help="Whether to ask for user confirmation when restarting kernel")
lexer_class = DottedObjectName(config=True,
help="The pygments lexer class to use."
)
def _lexer_class_changed(self, name, old, new):
lexer_class = import_item(new)
self.lexer = lexer_class()
def _lexer_class_default(self):
if py3compat.PY3:
return 'pygments.lexers.Python3Lexer'
else:
return 'pygments.lexers.PythonLexer'
lexer = Any()
def _lexer_default(self):
lexer_class = import_item(self.lexer_class)
return lexer_class()
# Emitted when a user visible 'execute_request' has been submitted to the
# kernel from the FrontendWidget. Contains the code to be executed.
executing = QtCore.Signal(object)
# Emitted when a user-visible 'execute_reply' has been received from the
# kernel and processed by the FrontendWidget. Contains the response message.
executed = QtCore.Signal(object)
# Emitted when an exit request has been received from the kernel.
exit_requested = QtCore.Signal(object)
_CallTipRequest = namedtuple('_CallTipRequest', ['id', 'pos'])
_CompletionRequest = namedtuple('_CompletionRequest',
['id', 'code', 'pos'])
_ExecutionRequest = namedtuple('_ExecutionRequest', ['id', 'kind'])
_local_kernel = False
_highlighter = Instance(FrontendHighlighter, allow_none=True)
# -------------------------------------------------------------------------
# 'Object' interface
# -------------------------------------------------------------------------
def __init__(self, local_kernel=_local_kernel, *args, **kw):
super(FrontendWidget, self).__init__(*args, **kw)
# FrontendWidget protected variables.
self._bracket_matcher = BracketMatcher(self._control)
self._call_tip_widget = CallTipWidget(self._control)
self._copy_raw_action = QtWidgets.QAction('Copy (Raw Text)', None)
self._hidden = False
self._highlighter = FrontendHighlighter(self, lexer=self.lexer)
self._kernel_manager = None
self._kernel_client = None
self._request_info = {}
self._request_info['execute'] = {}
self._callback_dict = {}
self._display_banner = True
# Configure the ConsoleWidget.
self.tab_width = 4
self._set_continuation_prompt('... ')
# Configure the CallTipWidget.
self._call_tip_widget.setFont(self.font)
self.font_changed.connect(self._call_tip_widget.setFont)
# Configure actions.
action = self._copy_raw_action
key = QtCore.Qt.CTRL | QtCore.Qt.SHIFT | QtCore.Qt.Key_C
action.setEnabled(False)
action.setShortcut(QtGui.QKeySequence(key))
action.setShortcutContext(QtCore.Qt.WidgetWithChildrenShortcut)
action.triggered.connect(self.copy_raw)
self.copy_available.connect(action.setEnabled)
self.addAction(action)
# Connect signal handlers.
document = self._control.document()
document.contentsChange.connect(self._document_contents_change)
# Set flag for whether we are connected via localhost.
self._local_kernel = local_kernel
# Whether or not a clear_output call is pending new output.
self._pending_clearoutput = False
#---------------------------------------------------------------------------
# 'ConsoleWidget' public interface
#---------------------------------------------------------------------------
def copy(self):
""" Copy the currently selected text to the clipboard, removing prompts.
"""
if self._page_control is not None and self._page_control.hasFocus():
self._page_control.copy()
elif self._control.hasFocus():
text = self._control.textCursor().selection().toPlainText()
if text:
# Remove prompts.
lines = text.splitlines()
lines = map(self._highlighter.transform_classic_prompt, lines)
lines = map(self._highlighter.transform_ipy_prompt, lines)
text = '\n'.join(lines)
# Needed to prevent errors when copying the prompt.
# See issue 264
try:
was_newline = text[-1] == '\n'
except IndexError:
was_newline = False
if was_newline: # user doesn't need newline
text = text[:-1]
QtWidgets.QApplication.clipboard().setText(text)
else:
self.log.debug("frontend widget : unknown copy target")
#---------------------------------------------------------------------------
# 'ConsoleWidget' abstract interface
#---------------------------------------------------------------------------
def _execute(self, source, hidden):
""" Execute 'source'. If 'hidden', do not show any output.
See parent class :meth:`execute` docstring for full details.
"""
msg_id = self.kernel_client.execute(source, hidden)
self._request_info['execute'][msg_id] = self._ExecutionRequest(msg_id, 'user')
self._hidden = hidden
if not hidden:
self.executing.emit(source)
def _prompt_started_hook(self):
""" Called immediately after a new prompt is displayed.
"""
if not self._reading:
self._highlighter.highlighting_on = True
def _prompt_finished_hook(self):
""" Called immediately after a prompt is finished, i.e. when some input
will be processed and a new prompt displayed.
"""
if not self._reading:
self._highlighter.highlighting_on = False
def _tab_pressed(self):
""" Called when the tab key is pressed. Returns whether to continue
processing the event.
"""
# Perform tab completion if:
# 1) The cursor is in the input buffer.
# 2) There is a non-whitespace character before the cursor.
# 3) There is no active selection.
text = self._get_input_buffer_cursor_line()
if text is None:
return False
non_ws_before = bool(text[:self._get_input_buffer_cursor_column()].strip())
complete = non_ws_before and self._get_cursor().selectedText() == ''
if complete:
self._complete()
return not complete
#---------------------------------------------------------------------------
# 'ConsoleWidget' protected interface
#---------------------------------------------------------------------------
def _context_menu_make(self, pos):
""" Reimplemented to add an action for raw copy.
"""
menu = super(FrontendWidget, self)._context_menu_make(pos)
for before_action in menu.actions():
if before_action.shortcut().matches(QtGui.QKeySequence.Paste) == \
QtGui.QKeySequence.ExactMatch:
menu.insertAction(before_action, self._copy_raw_action)
break
return menu
def request_interrupt_kernel(self):
if self._executing:
self.interrupt_kernel()
def request_restart_kernel(self):
message = 'Are you sure you want to restart the kernel?'
self.restart_kernel(message, now=False)
def _event_filter_console_keypress(self, event):
""" Reimplemented for execution interruption and smart backspace.
"""
key = event.key()
if self._control_key_down(event.modifiers(), include_command=False):
if key == QtCore.Qt.Key_C and self._executing:
self.request_interrupt_kernel()
return True
elif key == QtCore.Qt.Key_Period:
self.request_restart_kernel()
return True
elif not event.modifiers() & QtCore.Qt.AltModifier:
# Smart backspace: remove four characters in one backspace if:
# 1) everything left of the cursor is whitespace
# 2) the four characters immediately left of the cursor are spaces
if key == QtCore.Qt.Key_Backspace:
col = self._get_input_buffer_cursor_column()
cursor = self._control.textCursor()
if col > 3 and not cursor.hasSelection():
text = self._get_input_buffer_cursor_line()[:col]
if text.endswith(' ') and not text.strip():
cursor.movePosition(QtGui.QTextCursor.Left,
QtGui.QTextCursor.KeepAnchor, 4)
cursor.removeSelectedText()
return True
return super(FrontendWidget, self)._event_filter_console_keypress(event)
#---------------------------------------------------------------------------
# 'BaseFrontendMixin' abstract interface
#---------------------------------------------------------------------------
def _handle_clear_output(self, msg):
"""Handle clear output messages."""
if self.include_output(msg):
wait = msg['content'].get('wait', True)
if wait:
self._pending_clearoutput = True
else:
self.clear_output()
def _silent_exec_callback(self, expr, callback):
"""Silently execute `expr` in the kernel and call `callback` with reply
the `expr` is evaluated silently in the kernel (without) output in
the frontend. Call `callback` with the
`repr <http://docs.python.org/library/functions.html#repr> `_ as first argument
Parameters
----------
expr : string
valid string to be executed by the kernel.
callback : function
function accepting one argument, as a string. The string will be
the `repr` of the result of evaluating `expr`
The `callback` is called with the `repr()` of the result of `expr` as
first argument. To get the object, do `eval()` on the passed value.
See Also
--------
_handle_exec_callback : private method, deal with calling callback with reply
"""
# generate uuid, which would be used as an indication of whether or
# not the unique request originated from here (can use msg id ?)
local_uuid = str(uuid.uuid1())
msg_id = self.kernel_client.execute('',
silent=True, user_expressions={ local_uuid:expr })
self._callback_dict[local_uuid] = callback
self._request_info['execute'][msg_id] = self._ExecutionRequest(msg_id, 'silent_exec_callback')
def _handle_exec_callback(self, msg):
"""Execute `callback` corresponding to `msg` reply, after ``_silent_exec_callback``
Parameters
----------
msg : raw message send by the kernel containing an `user_expressions`
and having a 'silent_exec_callback' kind.
Notes
-----
This function will look for a `callback` associated with the
corresponding message id. Association has been made by
`_silent_exec_callback`. `callback` is then called with the `repr()`
of the value of corresponding `user_expressions` as argument.
`callback` is then removed from the known list so that any message
coming again with the same id won't trigger it.
"""
user_exp = msg['content'].get('user_expressions')
if not user_exp:
return
for expression in user_exp:
if expression in self._callback_dict:
self._callback_dict.pop(expression)(user_exp[expression])
def _handle_execute_reply(self, msg):
""" Handles replies for code execution.
"""
self.log.debug("execute_reply: %s", msg.get('content', ''))
msg_id = msg['parent_header']['msg_id']
info = self._request_info['execute'].get(msg_id)
# unset reading flag, because if execute finished, raw_input can't
# still be pending.
self._reading = False
# Note: If info is NoneType, this is ignored
if info and info.kind == 'user' and not self._hidden:
# Make sure that all output from the SUB channel has been processed
# before writing a new prompt.
self.kernel_client.iopub_channel.flush()
# Reset the ANSI style information to prevent bad text in stdout
# from messing up our colors. We're not a true terminal so we're
# allowed to do this.
if self.ansi_codes:
self._ansi_processor.reset_sgr()
content = msg['content']
status = content['status']
if status == 'ok':
self._process_execute_ok(msg)
elif status == 'aborted':
self._process_execute_abort(msg)
self._show_interpreter_prompt_for_reply(msg)
self.executed.emit(msg)
self._request_info['execute'].pop(msg_id)
elif info and info.kind == 'silent_exec_callback' and not self._hidden:
self._handle_exec_callback(msg)
self._request_info['execute'].pop(msg_id)
elif info and not self._hidden:
raise RuntimeError("Unknown handler for %s" % info.kind)
def _handle_error(self, msg):
""" Handle error messages.
"""
self._process_execute_error(msg)
def _handle_input_request(self, msg):
""" Handle requests for raw_input.
"""
self.log.debug("input: %s", msg.get('content', ''))
if self._hidden:
raise RuntimeError('Request for raw input during hidden execution.')
# Make sure that all output from the SUB channel has been processed
# before entering readline mode.
self.kernel_client.iopub_channel.flush()
def callback(line):
self._finalize_input_request()
self.kernel_client.input(line)
if self._reading:
self.log.debug("Got second input request, assuming first was interrupted.")
self._reading = False
self._readline(msg['content']['prompt'], callback=callback, password=msg['content']['password'])
def _kernel_restarted_message(self, died=True):
msg = "Kernel died, restarting" if died else "Kernel restarting"
self._append_html("<br>%s<hr><br>" % msg,
before_prompt=False
)
def _handle_kernel_died(self, since_last_heartbeat):
"""Handle the kernel's death (if we do not own the kernel).
"""
self.log.warning("kernel died: %s", since_last_heartbeat)
if self.custom_restart:
self.custom_restart_kernel_died.emit(since_last_heartbeat)
else:
self._kernel_restarted_message(died=True)
self.reset()
def _handle_kernel_restarted(self, died=True):
"""Notice that the autorestarter restarted the kernel.
There's nothing to do but show a message.
"""
self.log.warning("kernel restarted")
self._kernel_restarted_message(died=died)
self.reset()
def _handle_inspect_reply(self, rep):
"""Handle replies for call tips."""
self.log.debug("oinfo: %s", rep.get('content', ''))
cursor = self._get_cursor()
info = self._request_info.get('call_tip')
if info and info.id == rep['parent_header']['msg_id'] and \
info.pos == cursor.position():
content = rep['content']
if content.get('status') == 'ok' and content.get('found', False):
self._call_tip_widget.show_inspect_data(content)
def _handle_execute_result(self, msg):
""" Handle display hook output.
"""
self.log.debug("execute_result: %s", msg.get('content', ''))
if self.include_output(msg):
self.flush_clearoutput()
text = msg['content']['data']
self._append_plain_text(text + '\n', before_prompt=True)
def _handle_stream(self, msg):
""" Handle stdout, stderr, and stdin.
"""
self.log.debug("stream: %s", msg.get('content', ''))
if self.include_output(msg):
self.flush_clearoutput()
self.append_stream(msg['content']['text'])
def _handle_shutdown_reply(self, msg):
""" Handle shutdown signal, only if from other console.
"""
self.log.debug("shutdown: %s", msg.get('content', ''))
restart = msg.get('content', {}).get('restart', False)
if not self._hidden and not self.from_here(msg):
# got shutdown reply, request came from session other than ours
if restart:
# someone restarted the kernel, handle it
self._handle_kernel_restarted(died=False)
else:
# kernel was shutdown permanently
# this triggers exit_requested if the kernel was local,
# and a dialog if the kernel was remote,
# so we don't suddenly clear the qtconsole without asking.
if self._local_kernel:
self.exit_requested.emit(self)
else:
title = self.window().windowTitle()
reply = QtWidgets.QMessageBox.question(self, title,
"Kernel has been shutdown permanently. "
"Close the Console?",
QtWidgets.QMessageBox.Yes,QtWidgets.QMessageBox.No)
if reply == QtWidgets.QMessageBox.Yes:
self.exit_requested.emit(self)
def _handle_status(self, msg):
"""Handle status message"""
# This is where a busy/idle indicator would be triggered,
# when we make one.
state = msg['content'].get('execution_state', '')
if state == 'starting':
# kernel started while we were running
if self._executing:
self._handle_kernel_restarted(died=True)
elif state == 'idle':
pass
elif state == 'busy':
pass
def _started_channels(self):
""" Called when the KernelManager channels have started listening or
when the frontend is assigned an already listening KernelManager.
"""
self.reset(clear=True)
#---------------------------------------------------------------------------
# 'FrontendWidget' public interface
#---------------------------------------------------------------------------
def copy_raw(self):
""" Copy the currently selected text to the clipboard without attempting
to remove prompts or otherwise alter the text.
"""
self._control.copy()
def interrupt_kernel(self):
""" Attempts to interrupt the running kernel.
Also unsets _reading flag, to avoid runtime errors
if raw_input is called again.
"""
if self.custom_interrupt:
self._reading = False
self.custom_interrupt_requested.emit()
elif self.kernel_manager:
self._reading = False
self.kernel_manager.interrupt_kernel()
else:
self._append_plain_text('Cannot interrupt a kernel I did not start.\n')
def reset(self, clear=False):
""" Resets the widget to its initial state if ``clear`` parameter
is True, otherwise
prints a visual indication of the fact that the kernel restarted, but
does not clear the traces from previous usage of the kernel before it
was restarted. With ``clear=True``, it is similar to ``%clear``, but
also re-writes the banner and aborts execution if necessary.
"""
if self._executing:
self._executing = False
self._request_info['execute'] = {}
self._reading = False
self._highlighter.highlighting_on = False
if clear:
self._control.clear()
if self._display_banner:
self._append_plain_text(self.banner)
if self.kernel_banner:
self._append_plain_text(self.kernel_banner)
# update output marker for stdout/stderr, so that startup
# messages appear after banner:
self._show_interpreter_prompt()
def restart_kernel(self, message, now=False):
""" Attempts to restart the running kernel.
"""
# FIXME: now should be configurable via a checkbox in the dialog. Right
# now at least the heartbeat path sets it to True and the manual restart
# to False. But those should just be the pre-selected states of a
# checkbox that the user could override if so desired. But I don't know
# enough Qt to go implementing the checkbox now.
if self.custom_restart:
self.custom_restart_requested.emit()
return
if self.kernel_manager:
# Pause the heart beat channel to prevent further warnings.
self.kernel_client.hb_channel.pause()
# Prompt the user to restart the kernel. Un-pause the heartbeat if
# they decline. (If they accept, the heartbeat will be un-paused
# automatically when the kernel is restarted.)
if self.confirm_restart:
buttons = QtWidgets.QMessageBox.Yes | QtWidgets.QMessageBox.No
result = QtWidgets.QMessageBox.question(self, 'Restart kernel?',
message, buttons)
do_restart = result == QtWidgets.QMessageBox.Yes
else:
# confirm_restart is False, so we don't need to ask user
# anything, just do the restart
do_restart = True
if do_restart:
try:
self.kernel_manager.restart_kernel(now=now)
except RuntimeError as e:
self._append_plain_text(
'Error restarting kernel: %s\n' % e,
before_prompt=True
)
else:
self._append_html("<br>Restarting kernel...\n<hr><br>",
before_prompt=True,
)
else:
self.kernel_client.hb_channel.unpause()
else:
self._append_plain_text(
'Cannot restart a Kernel I did not start\n',
before_prompt=True
)
def append_stream(self, text):
"""Appends text to the output stream."""
self._append_plain_text(text, before_prompt=True)
def flush_clearoutput(self):
"""If a clearoutput is pending, execute it."""
if self._pending_clearoutput:
self._pending_clearoutput = False
self.clear_output()
def clear_output(self):
"""Clears the current line of output."""
cursor = self._control.textCursor()
cursor.beginEditBlock()
cursor.movePosition(cursor.StartOfLine, cursor.KeepAnchor)
cursor.insertText('')
cursor.endEditBlock()
#---------------------------------------------------------------------------
# 'FrontendWidget' protected interface
#---------------------------------------------------------------------------
def _auto_call_tip(self):
"""Trigger call tip automatically on open parenthesis
Call tips can be requested explcitly with `_call_tip`.
"""
cursor = self._get_cursor()
cursor.movePosition(QtGui.QTextCursor.Left)
if cursor.document().characterAt(cursor.position()) == '(':
# trigger auto call tip on open paren
self._call_tip()
def _call_tip(self):
"""Shows a call tip, if appropriate, at the current cursor location."""
# Decide if it makes sense to show a call tip
if not self.enable_calltips or not self.kernel_client.shell_channel.is_alive():
return False
cursor_pos = self._get_input_buffer_cursor_pos()
code = self.input_buffer
# Send the metadata request to the kernel
msg_id = self.kernel_client.inspect(code, cursor_pos)
pos = self._get_cursor().position()
self._request_info['call_tip'] = self._CallTipRequest(msg_id, pos)
return True
def _complete(self):
""" Performs completion at the current cursor location.
"""
code = self.input_buffer
cursor_pos = self._get_input_buffer_cursor_pos()
# Send the completion request to the kernel
msg_id = self.kernel_client.complete(code=code, cursor_pos=cursor_pos)
info = self._CompletionRequest(msg_id, code, cursor_pos)
self._request_info['complete'] = info
def _process_execute_abort(self, msg):
""" Process a reply for an aborted execution request.
"""
self._append_plain_text("ERROR: execution aborted\n")
def _process_execute_error(self, msg):
""" Process a reply for an execution request that resulted in an error.
"""
content = msg['content']
# If a SystemExit is passed along, this means exit() was called - also
# all the ipython %exit magic syntax of '-k' to be used to keep
# the kernel running
if content['ename']=='SystemExit':
keepkernel = content['evalue']=='-k' or content['evalue']=='True'
self._keep_kernel_on_exit = keepkernel
self.exit_requested.emit(self)
else:
traceback = ''.join(content['traceback'])
self._append_plain_text(traceback)
def _process_execute_ok(self, msg):
""" Process a reply for a successful execution request.
"""
payload = msg['content'].get('payload', [])
for item in payload:
if not self._process_execute_payload(item):
warning = 'Warning: received unknown payload of type %s'
print(warning % repr(item['source']))
def _process_execute_payload(self, item):
""" Process a single payload item from the list of payload items in an
execution reply. Returns whether the payload was handled.
"""
# The basic FrontendWidget doesn't handle payloads, as they are a
# mechanism for going beyond the standard Python interpreter model.
return False
def _show_interpreter_prompt(self):
""" Shows a prompt for the interpreter.
"""
self._show_prompt('>>> ')
def _show_interpreter_prompt_for_reply(self, msg):
""" Shows a prompt for the interpreter given an 'execute_reply' message.
"""
self._show_interpreter_prompt()
#------ Signal handlers ----------------------------------------------------
def _document_contents_change(self, position, removed, added):
""" Called whenever the document's content changes. Display a call tip
if appropriate.
"""
# Calculate where the cursor should be *after* the change:
position += added
document = self._control.document()
if position == self._get_cursor().position():
self._auto_call_tip()
#------ Trait default initializers -----------------------------------------
@default('banner')
def _banner_default(self):
""" Returns the standard Python banner.
"""
banner = 'Python %s on %s\nType "help", "copyright", "credits" or ' \
'"license" for more information.'
return banner % (sys.version, sys.platform)