PyReadline

2.1 · maintenance · verified Thu Apr 16

PyReadline (version 2.1) is a Python implementation of GNU readline functionality, primarily designed for Windows, to provide enhanced command-line editing features like history and tab completion. The project's last release was in 2015, and it is largely unmaintained. For users on Python 3.8 and newer, the community-maintained fork `pyreadline3` is the recommended alternative for compatible functionality.

Common errors

```
ModuleNotFoundError: No module named 'readline'
```
cause Attempting to import the `readline` module on Windows without `pyreadline` or `pyreadline3` installed, as `readline` is a POSIX-specific standard library module.

fix Install `pyreadline` (for older Python) or `pyreadline3` (for Python 3.8+) on Windows: `pip install pyreadline` or `pip install pyreadline3`.
```
AttributeError: module 'readline' has no attribute 'redisplay'
```
cause This often occurs when `pyreadline` is installed but an application or a specific interaction attempts to call a `readline` function that `pyreadline` either doesn't implement or hasn't correctly exposed/bound. This can also be a symptom of general incompatibility or an incomplete setup.

fix Ensure `pyreadline` is fully installed and try restarting the Python environment. If the issue persists, consider `pyreadline3` which might have better compatibility, or review specific usage patterns for `readline` features.
```
TypeError: 'type' object is not subscriptable (related to collections.Callable)
```
cause This error arises in Python 3.9 and later because `collections.Callable` was deprecated and then removed, replaced by `collections.abc.Callable`. PyReadline 2.1 uses the old path.

fix Upgrade to `pyreadline3`, which is designed for newer Python versions, or manually edit the `pyreadline` source to replace `collections.Callable` with `collections.abc.Callable`.

Warnings

breaking PyReadline 2.1 is not compatible with Python versions 3.10 and later. Users attempting to use it on these versions will encounter errors.
Fix: Migrate to `pyreadline3` (`pip install pyreadline3`) for Python 3.8+ compatibility, or use an older Python version.
deprecated The `pyreadline` project (version 2.1) has not been actively maintained since its last release in 2015. Many issues remain open, and it is considered stale.
Fix: For active development and compatibility with modern Python, use `pyreadline3`.
gotcha Python 3.9+ changed `collections.Callable` to `collections.abc.Callable`. Older `pyreadline` versions may raise `AttributeError` or `TypeError` due to this change if not patched.
Fix: Consider switching to `pyreadline3` which addresses this, or manually patch `Lib/site-packages/pyreadline/py3k_compat.py` to use `collections.abc.Callable`.
gotcha PyReadline is specifically for Windows environments. On POSIX systems, Python typically uses GNU readline directly, and attempting to install or use `pyreadline` can lead to conflicts or errors.
Fix: Only install `pyreadline` on Windows. On other operating systems, rely on the system's native readline implementation or use cross-platform alternatives like `prompt_toolkit`.

Install

pip install pyreadline Install PyReadline

Imports

readline
```
import readline
```
PyReadline, upon installation, creates a `readline.py` shim in site-packages to be imported as the standard `readline` module on Windows, allowing compatibility with modules like `rlcompleter`.

Quickstart

PyReadline primarily enhances the standard Python interactive prompt and the `input()` function on Windows. After installation, its features are generally active without explicit imports, though `import readline` will expose its API. This example demonstrates basic input and checks a `readline` function, noting potential compatibility issues with older versions.

import sys

# pyreadline enhances the built-in input() function on Windows
# if it's installed and correctly configured.
# The primary use is passive: install it, and your Python REPL
# and input() calls will have readline features.

print('Type something (with history and tab completion if pyreadline is active):')
try:
    user_input = input('>>> ')
    print(f'You typed: {user_input}')

    # Example of a readline function (available via the shim)
    # Requires pyreadline to be active and have bound these functions
    import readline
    # The following line might raise AttributeError if pyreadline isn't fully set up or patched
    print(f'Current history length: {readline.get_current_history_length()}')
except EOFError:
    print('\nExiting.')
except AttributeError as e:
    print(f'Readline attribute error: {e}. PyReadline might not be fully loaded or compatible with your Python version.')
except Exception as e:
    print(f'An unexpected error occurred: {e}')

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