Do not redefine _, linter complain.

It also confuse me as I search for `def _(` and there is no cost of
being explicit.

IPython/terminal/ptshell.py

@@ -1,462 +1,462 b''
 """IPython terminal interface using prompt_toolkit in place of readline"""
 from __future__ import print_function
 
 import os
 import sys
 import signal
 import unicodedata
 from warnings import warn
 from wcwidth import wcwidth
 
 from IPython.core.error import TryNext
 from IPython.core.interactiveshell import InteractiveShell
 from IPython.utils.py3compat import PY3, cast_unicode_py2, input
 from IPython.utils.terminal import toggle_set_term_title, set_term_title
 from IPython.utils.process import abbrev_cwd
 from traitlets import Bool, CBool, Unicode, Dict, Integer
 
 from prompt_toolkit.completion import Completer, Completion
 from prompt_toolkit.enums import DEFAULT_BUFFER, SEARCH_BUFFER, EditingMode
 from prompt_toolkit.filters import HasFocus, HasSelection, Condition, ViInsertMode, EmacsInsertMode
 from prompt_toolkit.history import InMemoryHistory
 from prompt_toolkit.shortcuts import create_prompt_application, create_eventloop, create_prompt_layout
 from prompt_toolkit.interface import CommandLineInterface
 from prompt_toolkit.key_binding.manager import KeyBindingManager
 from prompt_toolkit.keys import Keys
 from prompt_toolkit.layout.lexers import Lexer
 from prompt_toolkit.layout.lexers import PygmentsLexer
 from prompt_toolkit.styles import PygmentsStyle, DynamicStyle
 
 from pygments.styles import get_style_by_name, get_all_styles
 from pygments.lexers import Python3Lexer, BashLexer, PythonLexer
 from pygments.token import Token
 
 from .pt_inputhooks import get_inputhook_func
 from .interactiveshell import get_default_editor, TerminalMagics
 
 
 class IPythonPTCompleter(Completer):
     """Adaptor to provide IPython completions to prompt_toolkit"""
     def __init__(self, ipy_completer):
         self.ipy_completer = ipy_completer
 
     def get_completions(self, document, complete_event):
         if not document.current_line.strip():
             return
 
         used, matches = self.ipy_completer.complete(
                             line_buffer=document.current_line,
                             cursor_pos=document.cursor_position_col
         )
         start_pos = -len(used)
         for m in matches:
             m = unicodedata.normalize('NFC', m)
 
             # When the first character of the completion has a zero length,
             # then it's probably a decomposed unicode character. E.g. caused by
             # the "\dot" completion. Try to compose again with the previous
             # character.
             if wcwidth(m[0]) == 0:
                 if document.cursor_position + start_pos > 0:
                     char_before = document.text[document.cursor_position + start_pos - 1]
                     m = unicodedata.normalize('NFC', char_before + m)
 
                     # Yield the modified completion instead, if this worked.
                     if wcwidth(m[0:1]) == 1:
                         yield Completion(m, start_position=start_pos - 1)
                         continue
 
             # TODO: Use Jedi to determine meta_text
             # (Jedi currently has a bug that results in incorrect information.)
             # meta_text = ''
             # yield Completion(m, start_position=start_pos,
             #                  display_meta=meta_text)
             yield Completion(m, start_position=start_pos)
 
 class IPythonPTLexer(Lexer):
     """
     Wrapper around PythonLexer and BashLexer.
     """
     def __init__(self):
         self.python_lexer = PygmentsLexer(Python3Lexer if PY3 else PythonLexer)
         self.shell_lexer = PygmentsLexer(BashLexer)
 
     def lex_document(self, cli, document):
         if document.text.startswith('!'):
             return self.shell_lexer.lex_document(cli, document)
         else:
             return self.python_lexer.lex_document(cli, document)
 
 
 class TerminalInteractiveShell(InteractiveShell):
     colors_force = True
 
     space_for_menu = Integer(6, config=True, help='Number of line at the bottom of the screen '
                                                   'to reserve for the completion menu')
 
     def _space_for_menu_changed(self, old, new):
         self._update_layout()
 
     pt_cli = None
 
     autoedit_syntax = CBool(False, config=True,
                             help="auto editing of files with syntax errors.")
 
     confirm_exit = CBool(True, config=True,
         help="""
         Set to confirm when you try to exit IPython with an EOF (Control-D
         in Unix, Control-Z/Enter in Windows). By typing 'exit' or 'quit',
         you can force a direct exit without any confirmation.""",
     )
     editing_mode = Unicode('emacs', config=True,
         help="Shortcut style to use at the prompt. 'vi' or 'emacs'.",
     )
 
     mouse_support = Bool(False, config=True,
         help="Enable mouse support in the prompt"
     )
 
     highlighting_style = Unicode('default', config=True,
             help="The name of a Pygments style to use for syntax highlighting: \n %s" % ', '.join(get_all_styles())
     )
 
     def _highlighting_style_changed(self, old, new):
         self._style = self._make_style_from_name(self.highlighting_style)
 
     highlighting_style_overrides = Dict(config=True,
         help="Override highlighting format for specific tokens"
     )
 
     editor = Unicode(get_default_editor(), config=True,
         help="Set the editor used by IPython (default to $EDITOR/vi/notepad)."
     )
     
     term_title = Bool(True, config=True,
         help="Automatically set the terminal title"
     )
 
     display_completions_in_columns = Bool(False, config=True,
         help="Display a multi column completion menu.",
     )
 
     def _term_title_changed(self, name, new_value):
         self.init_term_title()
     
     def init_term_title(self):
         # Enable or disable the terminal title.
         if self.term_title:
             toggle_set_term_title(True)
             set_term_title('IPython: ' + abbrev_cwd())
         else:
             toggle_set_term_title(False)
 
     def get_prompt_tokens(self, cli):
         return [
             (Token.Prompt, 'In ['),
             (Token.PromptNum, str(self.execution_count)),
             (Token.Prompt, ']: '),
         ]
 
     def get_continuation_tokens(self, cli, width):
         return [
             (Token.Prompt, (' ' * (width - 5)) + '...: '),
         ]
 
     def init_prompt_toolkit_cli(self):
         if ('IPY_TEST_SIMPLE_PROMPT' in os.environ) or not sys.stdin.isatty():
             # Fall back to plain non-interactive output for tests.
             # This is very limited, and only accepts a single line.
             def prompt():
                 return cast_unicode_py2(input('In [%d]: ' % self.execution_count))
             self.prompt_for_code = prompt
             return
 
         kbmanager = KeyBindingManager.for_prompt()
         insert_mode = ViInsertMode() | EmacsInsertMode()
         # Ctrl+J == Enter, seemingly
         @kbmanager.registry.add_binding(Keys.ControlJ,
                             filter=(HasFocus(DEFAULT_BUFFER)
                                     & ~HasSelection()
                                     & insert_mode
                                    ))
         def _(event):
             b = event.current_buffer
             d = b.document
             if not (d.on_last_line or d.cursor_position_row >= d.line_count
                                            - d.empty_line_count_at_the_end()):
                 b.newline()
                 return
 
             status, indent = self.input_splitter.check_complete(d.text)
 
             if (status != 'incomplete') and b.accept_action.is_returnable:
                 b.accept_action.validate_and_handle(event.cli, b)
             else:
                 b.insert_text('\n' + (' ' * (indent or 0)))
 
         @kbmanager.registry.add_binding(Keys.ControlC, filter=HasFocus(DEFAULT_BUFFER))
-        def _(event):
+        def _reset_buffer(event):
             event.current_buffer.reset()
 
         @kbmanager.registry.add_binding(Keys.ControlC, filter=HasFocus(SEARCH_BUFFER))
-        def _(event):
+        def _reset_search_buffer(event):
             if event.current_buffer.document.text:
                 event.current_buffer.reset()
             else:
                 event.cli.push_focus(DEFAULT_BUFFER)
 
         supports_suspend = Condition(lambda cli: hasattr(signal, 'SIGTSTP'))
 
         @kbmanager.registry.add_binding(Keys.ControlZ, filter=supports_suspend)
-        def _(event):
+        def _suspend_to_bg(event):
             event.cli.suspend_to_background()
 
         @Condition
         def cursor_in_leading_ws(cli):
             before = cli.application.buffer.document.current_line_before_cursor
             return (not before) or before.isspace()
 
         # Ctrl+I == Tab
         @kbmanager.registry.add_binding(Keys.ControlI,
                             filter=(HasFocus(DEFAULT_BUFFER)
                                     & ~HasSelection()
                                     & insert_mode
                                     & cursor_in_leading_ws
                                    ))
-        def _(event):
+        def _indent_buffer(event):
             event.current_buffer.insert_text(' ' * 4)
 
         # Pre-populate history from IPython's history database
         history = InMemoryHistory()
         last_cell = u""
-        for _, _, cell in self.history_manager.get_tail(self.history_load_length,
+        for __, ___, cell in self.history_manager.get_tail(self.history_load_length,
                                                         include_latest=True):
             # Ignore blank lines and consecutive duplicates
             cell = cell.rstrip()
             if cell and (cell != last_cell):
                 history.append(cell)
 
         self._style = self._make_style_from_name(self.highlighting_style)
         style = DynamicStyle(lambda: self._style)
 
         editing_mode = getattr(EditingMode, self.editing_mode.upper())
 
         self._app = create_prompt_application(
                             editing_mode=editing_mode,
                             key_bindings_registry=kbmanager.registry,
                             history=history,
                             completer=IPythonPTCompleter(self.Completer),
                             enable_history_search=True,
                             style=style,
                             mouse_support=self.mouse_support,
                             **self._layout_options()
         )
         self.pt_cli = CommandLineInterface(self._app,
                            eventloop=create_eventloop(self.inputhook))
 
     def _make_style_from_name(self, name):
         """
         Small wrapper that make an IPython compatible style from a style name
 
         We need that to add style for prompt ... etc. 
         """
         style_cls = get_style_by_name(name)
         style_overrides = {
             Token.Prompt: '#009900',
             Token.PromptNum: '#00ff00 bold',
         }
         if name == 'default':
             style_cls = get_style_by_name('default')
             # The default theme needs to be visible on both a dark background
             # and a light background, because we can't tell what the terminal
             # looks like. These tweaks to the default theme help with that.
             style_overrides.update({
                 Token.Number: '#007700',
                 Token.Operator: 'noinherit',
                 Token.String: '#BB6622',
                 Token.Name.Function: '#2080D0',
                 Token.Name.Class: 'bold #2080D0',
                 Token.Name.Namespace: 'bold #2080D0',
             })
         style_overrides.update(self.highlighting_style_overrides)
         style = PygmentsStyle.from_defaults(pygments_style_cls=style_cls,
                                             style_dict=style_overrides)
 
         return style
 
     def _layout_options(self):
         """
         Return the current layout option for the current Terminal InteractiveShell
         """
         return {
                 'lexer':IPythonPTLexer(),
                 'reserve_space_for_menu':self.space_for_menu,
                 'get_prompt_tokens':self.get_prompt_tokens,
                 'get_continuation_tokens':self.get_continuation_tokens,
                 'multiline':True,
                 'display_completions_in_columns': self.display_completions_in_columns,
                 }
 
     def _update_layout(self):
         """
         Ask for a re computation of the application layout, if for example ,
         some configuration options have changed.
         """
         self._app.layout = create_prompt_layout(**self._layout_options())
 
     def prompt_for_code(self):
         document = self.pt_cli.run(
             pre_run=self.pre_prompt, reset_current_buffer=True)
         return document.text
 
     def init_io(self):
         if sys.platform not in {'win32', 'cli'}:
             return
 
         import colorama
         colorama.init()
 
         # For some reason we make these wrappers around stdout/stderr.
         # For now, we need to reset them so all output gets coloured.
         # https://github.com/ipython/ipython/issues/8669
         from IPython.utils import io
         io.stdout = io.IOStream(sys.stdout)
         io.stderr = io.IOStream(sys.stderr)
 
     def init_magics(self):
         super(TerminalInteractiveShell, self).init_magics()
         self.register_magics(TerminalMagics)
 
     def init_alias(self):
         # The parent class defines aliases that can be safely used with any
         # frontend.
         super(TerminalInteractiveShell, self).init_alias()
 
         # Now define aliases that only make sense on the terminal, because they
         # need direct access to the console in a way that we can't emulate in
         # GUI or web frontend
         if os.name == 'posix':
             for cmd in ['clear', 'more', 'less', 'man']:
                 self.alias_manager.soft_define_alias(cmd, cmd)
 
 
     def __init__(self, *args, **kwargs):
         super(TerminalInteractiveShell, self).__init__(*args, **kwargs)
         self.init_prompt_toolkit_cli()
         self.init_term_title()
         self.keep_running = True
 
     def ask_exit(self):
         self.keep_running = False
 
     rl_next_input = None
 
     def pre_prompt(self):
         if self.rl_next_input:
             self.pt_cli.application.buffer.text = cast_unicode_py2(self.rl_next_input)
             self.rl_next_input = None
 
     def interact(self):
         while self.keep_running:
             print(self.separate_in, end='')
 
             try:
                 code = self.prompt_for_code()
             except EOFError:
                 if (not self.confirm_exit) \
                         or self.ask_yes_no('Do you really want to exit ([y]/n)?','y','n'):
                     self.ask_exit()
 
             else:
                 if code:
                     self.run_cell(code, store_history=True)
                     if self.autoedit_syntax and self.SyntaxTB.last_syntax_error:
                         self.edit_syntax_error()
 
     def mainloop(self):
         # An extra layer of protection in case someone mashing Ctrl-C breaks
         # out of our internal code.
         while True:
             try:
                 self.interact()
                 break
             except KeyboardInterrupt:
                 print("\nKeyboardInterrupt escaped interact()\n")
 
     _inputhook = None
     def inputhook(self, context):
         if self._inputhook is not None:
             self._inputhook(context)
 
     def enable_gui(self, gui=None):
         if gui:
             self._inputhook = get_inputhook_func(gui)
         else:
             self._inputhook = None
 
     # Methods to support auto-editing of SyntaxErrors:
 
     def edit_syntax_error(self):
         """The bottom half of the syntax error handler called in the main loop.
 
         Loop until syntax error is fixed or user cancels.
         """
 
         while self.SyntaxTB.last_syntax_error:
             # copy and clear last_syntax_error
             err = self.SyntaxTB.clear_err_state()
             if not self._should_recompile(err):
                 return
             try:
                 # may set last_syntax_error again if a SyntaxError is raised
                 self.safe_execfile(err.filename, self.user_ns)
             except:
                 self.showtraceback()
             else:
                 try:
                     with open(err.filename) as f:
                         # This should be inside a display_trap block and I
                         # think it is.
                         sys.displayhook(f.read())
                 except:
                     self.showtraceback()
 
     def _should_recompile(self, e):
         """Utility routine for edit_syntax_error"""
 
         if e.filename in ('<ipython console>', '<input>', '<string>',
                           '<console>', '<BackgroundJob compilation>',
                           None):
             return False
         try:
             if (self.autoedit_syntax and
                     not self.ask_yes_no(
                         'Return to editor to correct syntax error? '
                         '[Y/n] ', 'y')):
                 return False
         except EOFError:
             return False
 
         def int0(x):
             try:
                 return int(x)
             except TypeError:
                 return 0
 
         # always pass integer line and offset values to editor hook
         try:
             self.hooks.fix_error_editor(e.filename,
                                         int0(e.lineno), int0(e.offset),
                                         e.msg)
         except TryNext:
             warn('Could not open editor')
             return False
         return True
 
     # Run !system commands directly, not through pipes, so terminal programs
     # work correctly.
     system = InteractiveShell.system_raw
 
 
 if __name__ == '__main__':
     TerminalInteractiveShell.instance().interact()