readline --- GNU readline interface

The 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 rlcompleter module, which supports completion of Python identifiers at the interactive prompt. Settings made using this module affect the behaviour of both the interpreter's interactive prompt and the prompts offered by the built-in input() function.

Readline keybindings may be configured via an initialization file, typically .inputrc in your home directory. See Readline Init File in the GNU Readline manual for information about the format and allowable constructs of that file, and the capabilities of the Readline library in general.

Disponibilité: not Android, not iOS, not WASI.

This module is not supported on mobile platforms or WebAssembly platforms.

This is an optional module. If it is missing from your copy of CPython, look for documentation from your distributor (that is, whoever provided Python to you). If you are the distributor, see Requirements for optional modules.

Note

The underlying Readline library API may be implemented by the editline (libedit) library instead of GNU readline. On macOS the readline module detects which library is being used at run time.

The configuration file for editline is different from that of GNU readline. If you programmatically load configuration strings you can use backend to determine which library is being used.

If you use editline/libedit readline emulation on macOS, the initialization file located in your home directory is named .editrc. For example, the following content in ~/.editrc will turn ON vi keybindings and TAB completion:

python:bind -v
python:bind ^I rl_complete

Also note that different libraries may use different history file formats. When switching the underlying library, existing history files may become unusable.

readline.backend

The name of the underlying Readline library being used, either "readline" or "editline".

Ajouté dans la version 3.13.

Fichier d'initialisation

Les fonctions suivantes se rapportent au fichier d'initialisation et à la configuration utilisateur :

readline.parse_and_bind(string)

Execute the init line provided in the string argument. This calls rl_parse_and_bind() in the underlying library.

readline.read_init_file([filename])

Execute a readline initialization file. The default filename is the last filename used. This calls rl_read_init_file() in the underlying library. It raises an auditing event open with the file name if given, and "<readline_init_file>" otherwise, regardless of which file the library resolves.

Modifié dans la version 3.14: The auditing event was added.

Tampon de ligne

Les fonctions suivantes opèrent sur le tampon de ligne :

readline.get_line_buffer()

Return the current contents of the line buffer (rl_line_buffer in the underlying library).

readline.insert_text(string)

Insert text into the line buffer at the cursor position. This calls rl_insert_text() in the underlying library, but ignores the return value.

readline.redisplay()

Change what's displayed on the screen to reflect the current contents of the line buffer. This calls rl_redisplay() in the underlying library.

Fichier d'historique

les fonctions suivantes opèrent sur un fichier d'historique :

readline.read_history_file([filename])

Load a readline history file, and append it to the history list. The default filename is ~/.history. This calls read_history() in the underlying library and raises an auditing event open with the file name if given and "~/.history" otherwise.

Modifié dans la version 3.14: The auditing event was added.

readline.write_history_file([filename])

Save the history list to a readline history file, overwriting any existing file. The default filename is ~/.history. This calls write_history() in the underlying library and raises an auditing event open with the file name if given and "~/.history" otherwise.

Modifié dans la version 3.14: The auditing event was added.

readline.append_history_file(nelements[, filename])

Append the last nelements items of history to a file. The default filename is ~/.history. The file must already exist. This calls append_history() in the underlying library. This function only exists if Python was compiled for a version of the library that supports it. It raises an auditing event open with the file name if given and "~/.history" otherwise.

Ajouté dans la version 3.5.

Modifié dans la version 3.14: The auditing event was added.

readline.get_history_length()
readline.set_history_length(length)

Set or return the desired number of lines to save in the history file. The write_history_file() function uses this value to truncate the history file, by calling history_truncate_file() in the underlying library. Negative values imply unlimited history file size.

Liste d'historique

Les fonctions suivantes opèrent sur une liste d'historique globale :

readline.clear_history()

Clear the current history. This calls clear_history() in the underlying library. The Python function only exists if Python was compiled for a version of the library that supports it.

readline.get_current_history_length()

Renvoie le nombre d'objets actuellement dans l'historique. (C'est différent de get_history_length(), qui renvoie le nombre maximum de lignes qui vont être écrites dans un fichier d'historique.)

readline.get_history_item(index)

Return the current contents of history item at index. The item index is one-based. This calls history_get() in the underlying library.

readline.remove_history_item(pos)

Remove history item specified by its position from the history. The position is zero-based. This calls remove_history() in the underlying library.

readline.replace_history_item(pos, line)

Replace history item specified by its position with line. The position is zero-based. This calls replace_history_entry() in the underlying library.

readline.add_history(line)

Append line to the history buffer, as if it was the last line typed. This calls add_history() in the underlying library.

readline.set_auto_history(enabled)

Enable or disable automatic calls to add_history() when reading input via readline. The enabled argument should be a Boolean value that when true, enables auto history, and that when false, disables auto history.

Ajouté dans la version 3.6.

Particularité de l'implémentation CPython : Auto history is enabled by default, and changes to this do not persist across multiple sessions.

Fonctions de rappel au démarrage

readline.set_startup_hook([function])

Set or remove the function invoked by the rl_startup_hook callback of the underlying library. If function is specified, it will be used as the new hook function; if omitted or None, any function already installed is removed. The hook is called with no arguments just before readline prints the first prompt.

readline.set_pre_input_hook([function])

Set or remove the function invoked by the rl_pre_input_hook callback of the underlying library. If function is specified, it will be used as the new hook function; if omitted or None, any function already installed is removed. The hook is called with no arguments after the first prompt has been printed and just before readline starts reading input characters. This function only exists if Python was compiled for a version of the library that supports it.

readline.get_pre_input_hook()

Get the current pre-input hook function, or None if no pre-input hook function has been set. This function only exists if Python was compiled for a version of the library that supports it.

Ajouté dans la version 3.15.

Complétion

The following functions relate to implementing a custom word completion function. This is typically operated by the Tab key, and can suggest and automatically complete a word being typed. By default, Readline is set up to be used by rlcompleter to complete Python identifiers for the interactive interpreter. If the readline module is to be used with a custom completer, a different set of word delimiters should be set.

readline.set_completer([function])

Définit ou supprime la fonction de complétion. Si function est spécifié, il sera utilisé en tant que nouvelle fonction de complétion; si omis ou None, toute fonction de complétion déjà installé est supprimé. La fonction de complétion est appelée telle que function(text, state), pour state valant 0, 1, 2, ..., jusqu'à ce qu'elle renvoie une valeur qui n'est pas une chaîne de caractères. Elle doit renvoyer les prochaines complétions possibles commençant par text.

The installed completer function is invoked by the entry_func callback passed to rl_completion_matches() in the underlying library. The text string comes from the first parameter to the rl_attempted_completion_function callback of the underlying library.

readline.get_completer()

Récupère la fonction de complétion, ou None si aucune fonction de complétion n'a été définie.

readline.get_completion_type()

Get the type of completion being attempted. This returns the rl_completion_type variable in the underlying library as an integer.

readline.get_begidx()
readline.get_endidx()

Get the beginning or ending index of the completion scope. These indexes are the start and end arguments passed to the rl_attempted_completion_function callback of the underlying library. The values may be different in the same input editing scenario based on the underlying C readline implementation. Ex: libedit is known to behave differently than libreadline.

readline.set_completer_delims(string)
readline.get_completer_delims()

Set or get the word delimiters for completion. These determine the start of the word to be considered for completion (the completion scope). These functions access the rl_completer_word_break_characters variable in the underlying library.

readline.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. This sets or clears the rl_completion_display_matches_hook callback in the underlying library. The completion display function is called as function(substitution, [matches], longest_match_length) once each time matches need to be displayed.

Exemple

The following example demonstrates how to use the readline module's history reading and writing functions to automatically load and save a history file named .python_history from the user's home directory. The code below would normally be executed automatically during interactive sessions from the user's PYTHONSTARTUP file.

import atexit
import os
import readline

histfile = os.path.join(os.path.expanduser("~"), ".python_history")
try:
    readline.read_history_file(histfile)
    # default history len is -1 (infinite), which may grow unruly
    readline.set_history_length(1000)
except FileNotFoundError:
    pass

atexit.register(readline.write_history_file, histfile)

Ce code est en réalité automatiquement exécuté lorsque Python tourne en mode interactif (voir Readline configuration).

L'exemple suivant atteint le même objectif mais gère des sessions interactives concurrentes, en ajoutant seulement le nouvel historique.

import atexit
import os
import readline
histfile = os.path.join(os.path.expanduser("~"), ".python_history")

try:
    readline.read_history_file(histfile)
    h_len = readline.get_current_history_length()
except FileNotFoundError:
    open(histfile, 'wb').close()
    h_len = 0

def save(prev_h_len, histfile):
    new_h_len = readline.get_current_history_length()
    readline.set_history_length(1000)
    readline.append_history_file(new_h_len - prev_h_len, histfile)
atexit.register(save, h_len, histfile)

L'exemple suivant étend la classe code.InteractiveConsole pour gérer la sauvegarde/restauration de l'historique.

import atexit
import code
import os
import readline

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 FileNotFoundError:
                pass
            atexit.register(self.save_history, histfile)

    def save_history(self, histfile):
        readline.set_history_length(1000)
        readline.write_history_file(histfile)

Note

The new REPL introduced in version 3.13 doesn't support readline. However, readline can still be used by setting the PYTHON_BASIC_REPL environment variable.