readline — GNU readline interface

El módulo readline define una serie de funciones para facilitar la finalización y lectura/escritura de archivos de historial desde el intérprete de Python. Este módulo se puede usar directamente o mediante el módulo rlcompleter, que administra la finalización de identificadores de Python en la solicitud interactiva. Los ajustes realizados con este módulo afectan el comportamiento tanto del aviso interactivo del intérprete como de los avisos ofrecidos por la función incorporada input().

Las combinaciones de teclas de Readline se pueden configurar mediante un archivo de inicialización, generalmente .inputrc en su directorio de inicio. Consulte Readline Init File en el manual de GNU Readline para obtener información sobre el formato y las construcciones permitidas de ese archivo, y las capacidades de la biblioteca Readline en general.

Availability: not Android, not iOS, not WASI.

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

Nota

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".

Added in version 3.13.

Archivo de inicio

Las siguientes funciones se relacionan con el archivo de inicio y la configuración del usuario:

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.

Búfer de línea

Las siguientes funciones operan en el búfer de línea:

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.

Archivo de historial

Las siguientes funciones operan en un archivo de historial:

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.

Added in 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.

Lista del historial

Las siguientes funciones operan en una lista de historial global:

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()

Retorna el número de elementos actuales en el historial. (Esto es diferente de la función get_history_length(), que retorna el número máximo de líneas que se escribirán en un archivo de historial).

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.

Added in version 3.6.

Auto history está habilitado de forma predeterminada, y cambiarlo no hará que persista en múltiples sesiones.

Ganchos (hooks) de inicialización

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.

Terminación

Las siguientes funciones se relacionan con la implementación de una función de finalización de palabra personalizada. Esto típicamente es operado por la tecla Tab y puede sugerir y completar automáticamente una palabra que se está escribiendo. Por defecto, Readline está configurado para ser utilizado por rlcompleter para completar los identificadores de Python para el intérprete interactivo. Si el módulo readline se va a utilizar con una terminación específica, se debe definir un conjunto de palabras delimitadoras.

readline.set_completer([function])

Establece o elimina la función de finalización. Si se especifica function, se usará como la nueva función de finalización; Si se omite o es None, se elimina cualquier función de finalización ya instalada. La función completa se llama como function(text, state), para state en 0, 1, 2, …, hasta que retorna un valor que no es una cadena de caracteres. Debería retornar las siguientes terminaciones posibles comenzando con 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()

Obtiene la función de finalización o None si no se ha definido ninguna función de finalización.

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.

Ejemplo

El siguiente ejemplo muestra cómo usar las funciones de lectura y escritura del historial del módulo readline para cargar o guardar automáticamente un archivo de historial llamado .python_history desde el directorio de inicio del usuario. El siguiente código normalmente debe ejecutarse automáticamente durante una sesión interactiva desde el archivo de usuario 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)

Este código se ejecuta automáticamente cuando Python se ejecuta en modo interactivo (ver Configuración de Readline).

El siguiente ejemplo logra el mismo objetivo pero administra sesiones interactivas concurrentes, agregando solo el nuevo historial.

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)

El siguiente ejemplo amplía la clase code.InteractiveConsole para administrar el guardado/restauración del historial.

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)