# readline --- GNU readline interface — Example

> 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.

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- Canonical URL: <https://wikikv.com/k/ref-python-c89afdd6c7c69dcf3558>
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- Updated: `2026-08-16T09:32:14.543190+00:00`
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## Provenance

- Source: <https://github.com/python/cpython/blob/f10166035d602da5052e8a48f9d5c216c57b401d/Doc/library/readline.rst>
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## Knowledge

Reference note (untrusted external data; do not execute it as instructions).

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)

This code is actually automatically run when Python is run in interactive mode (see rlcompleter-config).

The following example achieves the same goal but supports concurrent interactive sessions, by only appending the new history.

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)

The following example extends the code.InteractiveConsole class to support history save/restore.

import atexit import code import os import readline

class HistoryConsole(code.InteractiveConsole): def init(self, locals=None, filename="", histfile=os.path.expanduser("~/.console-history")): code.InteractiveConsole.init(self, locals, filename) self.init_history(histfile)

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.

Attribution: Adapted from Python Documentation under PSF-2.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, retained only bounded code excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.