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:mod:`readline` --- GNU readline interface
==========================================
.. module:: readline
:platform: Unix
:synopsis: GNU readline support for Python.
.. sectionauthor:: Skip Montanaro <skip@pobox.com>
The :mod:`readline` module defines a number of functions to facilitate
completion and reading/writing of history files from the Python interpreter.
This module can be used directly or via the :mod:`rlcompleter` module. Settings
made using this module affect the behaviour of both the interpreter's
interactive prompt and the prompts offered by the :func:`raw_input` and
:func:`input` built-in functions.
.. note::
On MacOS X the :mod:`readline` module can be implemented using
the ``libedit`` library instead of GNU readline.
The configuration file for ``libedit`` is different from that
of GNU readline. If you programmaticly load configuration strings
you can check for the text "libedit" in :const:`readline.__doc__`
to differentiate between GNU readline and libedit.
The :mod:`readline` module defines the following functions:
.. function:: parse_and_bind(string)
Parse and execute single line of a readline init file.
.. function:: get_line_buffer()
Return the current contents of the line buffer.
.. function:: insert_text(string)
Insert text into the command line.
.. function:: read_init_file([filename])
Parse a readline initialization file. The default filename is the last filename
used.
.. function:: read_history_file([filename])
Load a readline history file. The default filename is :file:`~/.history`.
.. function:: write_history_file([filename])
Save a readline history file. The default filename is :file:`~/.history`.
.. function:: clear_history()
Clear the current history. (Note: this function is not available if the
installed version of GNU readline doesn't support it.)
.. versionadded:: 2.4
.. function:: get_history_length()
Return the desired length of the history file. Negative values imply unlimited
history file size.
.. function:: set_history_length(length)
Set the number of lines to save in the history file. :func:`write_history_file`
uses this value to truncate the history file when saving. Negative values imply
unlimited history file size.
.. function:: get_current_history_length()
Return the number of lines currently in the history. (This is different from
:func:`get_history_length`, which returns the maximum number of lines that will
be written to a history file.)
.. versionadded:: 2.3
.. function:: get_history_item(index)
Return the current contents of history item at *index*.
.. versionadded:: 2.3
.. function:: remove_history_item(pos)
Remove history item specified by its position from the history.
.. versionadded:: 2.4
.. function:: replace_history_item(pos, line)
Replace history item specified by its position with the given line.
.. versionadded:: 2.4
.. function:: redisplay()
Change what's displayed on the screen to reflect the current contents of the
line buffer.
.. versionadded:: 2.3
.. function:: set_startup_hook([function])
Set or remove the startup_hook function. If *function* is specified, it will be
used as the new startup_hook function; if omitted or ``None``, any hook function
already installed is removed. The startup_hook function is called with no
arguments just before readline prints the first prompt.
.. function:: set_pre_input_hook([function])
Set or remove the pre_input_hook function. If *function* is specified, it will
be used as the new pre_input_hook function; if omitted or ``None``, any hook
function already installed is removed. The pre_input_hook function is called
with no arguments after the first prompt has been printed and just before
readline starts reading input characters.
.. function:: set_completer([function])
Set or remove the completer function. If *function* is specified, it will be
used as the new completer function; if omitted or ``None``, any completer
function already installed is removed. The completer function is called as
``function(text, state)``, for *state* in ``0``, ``1``, ``2``, ..., until it
returns a non-string value. It should return the next possible completion
starting with *text*.
.. function:: get_completer()
Get the completer function, or ``None`` if no completer function has been set.
.. versionadded:: 2.3
.. function:: get_completion_type()
Get the type of completion being attempted.
.. versionadded:: 2.6
.. function:: get_begidx()
Get the beginning index of the readline tab-completion scope.
.. function:: get_endidx()
Get the ending index of the readline tab-completion scope.
.. function:: set_completer_delims(string)
Set the readline word delimiters for tab-completion.
.. function:: get_completer_delims()
Get the readline word delimiters for tab-completion.
.. function:: set_completion_display_matches_hook([function])
Set or remove the completion display function. If *function* is
specified, it will be used as the new completion display function;
if omitted or ``None``, any completion display function already
installed is removed. The completion display function is called as
``function(substitution, [matches], longest_match_length)`` once
each time matches need to be displayed.
.. versionadded:: 2.6
.. function:: add_history(line)
Append a line to the history buffer, as if it was the last line typed.
.. seealso::
Module :mod:`rlcompleter`
Completion of Python identifiers at the interactive prompt.
.. _readline-example:
Example
-------
The following example demonstrates how to use the :mod:`readline` module's
history reading and writing functions to automatically load and save a history
file named :file:`.pyhist` from the user's home directory. The code below would
normally be executed automatically during interactive sessions from the user's
:envvar:`PYTHONSTARTUP` file. ::
import os
histfile = os.path.join(os.environ["HOME"], ".pyhist")
try:
readline.read_history_file(histfile)
except IOError:
pass
import atexit
atexit.register(readline.write_history_file, histfile)
del os, histfile
The following example extends the :class:`code.InteractiveConsole` class to
support history save/restore. ::
import code
import readline
import atexit
import os
class HistoryConsole(code.InteractiveConsole):
def __init__(self, locals=None, filename="<console>",
histfile=os.path.expanduser("~/.console-history")):
code.InteractiveConsole.__init__(self, locals, filename)
self.init_history(histfile)
def init_history(self, histfile):
readline.parse_and_bind("tab: complete")
if hasattr(readline, "read_history_file"):
try:
readline.read_history_file(histfile)
except IOError:
pass
atexit.register(self.save_history, histfile)
def save_history(self, histfile):
readline.write_history_file(histfile)
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