# `readline` --- GNU readline interface

Le module `readline` définit des fonctions pour faciliter la complétion et la lecture/écriture des fichiers d'historique depuis l'interpréteur Python. Ce module peut être utilisé directement, ou depuis le module `rlcompleter`, qui gère la complétion des mots clefs dans l'invite de commande interactive. Les paramétrages faits en utilisant ce module affectent à la fois le comportement de l'invite de commande interactive et l'invite de commande fournie par la fonction native `input()`.

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.

Availability: not Android, not iOS, not WASI.

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

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.

## 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.

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.

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.

  Ajouté dans la version 3.5.

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.

## Complétion

Les fonctions suivantes relatent comment implémenter une fonction de complétion d'un mot spécifique. C'est typiquement déclenché par la touche Tab, et peut suggérer et automatiquement compléter un mot en cours de saisie. Par défaut, Readline est configuré pour être utilisé par `rlcompleter` pour compléter les mots clefs de Python pour l'interpréteur interactif. Si le module `readline` doit être utilisé avec une complétion spécifique, un ensemble de mots délimiteurs doivent être définis.

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

L'exemple suivant démontre comment utiliser les fonctions de lecture et d'écriture de l'historique du module `readline` pour charger ou sauvegarder automatiquement un fichier d'historique nommé `.python_history` depuis le répertoire d’accueil de l’utilisateur. Le code ci-dessous doit normalement être exécuté automatiquement durant une session interactive depuis le fichier de l'utilisateur `PYTHONSTARTUP`.

    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)