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Alternative Python bindings for GNU Readline

Project description


The GNU Readline Library is the canonical implementation of command line editing, tab completion, and history for console-based applications. It is developed as part of Bash and available on virtually any platform.

While Python ships with readline bindings in its standard library, they only implement a subset of readline’s features, just enough to perform identifier completion at the Python interpreter prompt.

The rl package aims to provide full implementations of GNU Readline’s Custom Completer and History interfaces. It also contains high-level APIs to better organize the namespace and shield applications from low-level verbosity.

Package Contents

rl exports these components:

Interface to the readline completer. Used to configure the completion aspects of readline.
Interface to the active readline completion. Used to interact with readline when a completion is in progress.
A factory turning any callable into a completion entry function that can be handed to readline.
A decorator printing exceptions to stderr. Useful when writing Python completions and hooks, as exceptions occurring there are usually swallowed by the in-between C code.
Interface to the readline history. Used to read and write history files and to manipulate history entries.
The readline bindings module. Contains everything known from the standard library plus extensions specific to the rl package. The completer, completion, and history interfaces make use of this module, and you should rarely need to interact with it directly.

For further details please refer to the API Documentation.

Example Code

The code below implements system command completion similar to Bash:

import os
from rl import completer
from rl import generator

def complete_command(text):
    # Return executables matching 'text'
    for dir in os.environ.get('PATH').split(':'):
        dir = os.path.expanduser(dir)
        if os.path.isdir(dir):
            for name in os.listdir(dir):
                if name.startswith(text):
                    if os.access(os.path.join(dir, name), os.R_OK|os.X_OK):
                        yield name

def main():
    # Set the completion function
    completer.completer = generator(complete_command)

    # Enable TAB completion
    completer.parse_and_bind('TAB: complete')

    command = raw_input('command> ')
    print 'You typed:', command

More examples are included in the package source. Also see gpgkeys, a front-end for GnuPG built entirely around tab completion.


rl development is hosted on GitHub where it also has an issue tracker.


rl requires Python 2.5 or higher and GNU Readline 5.0 or higher.

On Linux, install libreadline6-dev before attempting to build rl. On Mac OS X, make sure you have Xcode Tools installed. Then type:

easy_install rl

and watch the console. When it reads:

Finished processing dependencies for rl

you are done and rl is ready to use.

Static Builds

Normally, rl.readline will attempt to link against your system’s libreadline. If this is not possible, notably on Mac OS X which ships with libedit, a static version of GNU Readline 6.2 is built.

To force a static build, set the RL_BUILD_STATIC_READLINE environment variable.


2.4 - 2012-10-05

  • Update to Python 3.3 Unicode C-API. [stefan]

2.3 - 2012-07-18

  • Implement history iterators in C instead of relying on intermediate lists. [stefan]
  • Raise a more informative error when history slicing is attempted. [stefan]

2.2 - 2012-05-10

  • Restore support for gcc < 4.2. [stefan]
  • Switch to a happier looking Sphinx theme. [stefan]

2.1 - 2012-04-27

  • Force a static build if the RL_BUILD_STATIC_READLINE environment variable is set. [stefan]
  • Include readline 6.2 patches in static builds. [stefan]
  • Suppress compiler warnings on more platforms. [stefan]

2.0.1 - 2011-10-06

  • Fix a C compiler issue under Python 3 on Linux. [stefan]

2.0 - 2011-10-06

  • Drop support for cmd.Cmd. You now must derive your command interpreters from kmd.Kmd to use rl features. [stefan]
  • Accept None as argument to file operations under Python 3. [stefan]
  • Switch to pretty Sphinx-based docs. [stefan]

1.16 - 2011-07-28

  • Tilde-expand filenames in read_history_file and write_history_file. [stefan]

1.15.2 - 2011-07-03

  • Silence a second C compiler warning in function get_y_or_n. [stefan]

1.15.1 - 2011-07-03

  • Silence a C compiler warning in function get_y_or_n. [stefan]

1.15 - 2011-06-04

  • Fix memory leaks in py_remove_history, py_replace_history, and py_clear_history which can occur when history entries are edited. See Python issue 12186. [stefan]
  • Add a default display_matches_hook that behaves exactly like readline behaves in Bash. [stefan]
  • Add reset functions to completer, completion, and history. [stefan]

1.14 - 2011-05-05

  • Add xfree.c to sources when building GNU Readline 6.2. [stefan]
  • Allow history indexes of type long. [stefan]

1.13 - 2011-03-11

  • Use a custom build_ext command to find the best termcap library. [stefan]
  • Update static builds to GNU Readline 6.2. [stefan]

1.12 - 2010-08-04

  • Fix memory leaks in py_remove_history and py_replace_history. See Python issue 9450. [stefan]

1.11 - 2010-05-21

  • Update README, API documentation, and examples. [stefan]
  • MacPython detection caught other framework builds as well. [stefan]

1.10 - 2010-05-05

  • Rework the history interface: Implement iteration and remove redundant APIs. [stefan]
  • History stifling could cause duplicate history entries. [stefan]
  • Make sure begidx and endidx completion variables are reset to 0. [stefan]

1.9 - 2010-04-02

  • Remove unused defines; we don’t support libedit or readline < 5.0. [stefan]
  • Improve performance of get_current_history_length. [stefan]

1.8 - 2010-03-14

  • Make get_history_item zero-based and remove get_history_base. [stefan]

1.7 - 2010-03-09

  • Support installation into MacPython for Mac OS X. [stefan]

1.6 - 2010-03-07

  • The history size can now be limited (“stifled”) by setting history.max_entries. This supersedes history.length which has been removed. [stefan]
  • Close a memory leak in get_current_history_length. Also see Python issue 8065. [stefan]

1.5.4 - 2010-03-01

  • Avoid segfaults during codec lookup by calling PyGILState_Ensure in all the right places. Fixes rl issue/5. Removes the workaround introduced in 1.5.2. [stefan]

1.5.3 - 2010-02-26

  • Re-release with link to the correct issue. [stefan]

1.5.2 - 2010-02-26

  • Work around segfaults under Python 3 on Linux, which are caused by bad or missing codecs. This restricts Linux to UTF-8 and Latin-1 locales only. Also see rl issue/5. [stefan]

1.5.1 - 2010-02-25

  • Switch readline download location to for speed. [stefan]

1.5 - 2010-02-25

  • In Python 3, convert to and from Unicode using filesystem encoding and “surrogateescape” error handler. See PEP 383 for the low-down. [stefan]

1.4.1 - 2010-02-13

  • Fix GPL trove classifier. [stefan]

1.4 - 2010-02-13

  • rl can now be installed into the system Python on Mac OS X, the only dependency being Xcode Tools. [stefan]
  • Change license to PSF or GPL. [stefan]

1.3 - 2010-01-03

  • Fix header detection under Fink on Mac OS X. [stefan]
  • Add readline_version API. [stefan]

1.2 - 2009-11-24

  • Improve API documentation and examples. [stefan]

1.1 - 2009-11-16

  • Remove all occurrences of old-style function typedefs to silence compiler warnings. [stefan]
  • Make the display_matches_hook work in Python 2.5. Fixes rl issue/1. [stefan]
  • No longer auto-refresh the prompt at the end of display_match_list. Applications should call redisplay(force=True) to restore the prompt. [stefan]

1.0 - 2009-11-08

  • No changes since 1.0a8.

1.0a8 - 2009-11-07

  • Close a memory leak in word_break_hook. Three cheers for Xcode’s leaks tool. [stefan]

1.0a7 - 2009-11-05

  • Rename _readline module to readline since it’s not private. [stefan]
  • Remove dump and read_key APIs from public interfaces. [stefan]

1.0a6 - 2009-10-30

  • Unclutter the completer interface by removing settings that can just as well be made with parse_and_bind. [stefan]
  • Fix a memory leak in username_completion_function and filename_completion_function. [stefan]
  • Add a custom epydoc stylesheet to make its reST rendering more pleasant. [stefan]

1.0a5 - 2009-10-29

  • Make all completion properties writable. While not useful in production, this allows us to write better tests. [stefan]
  • Improve API documentation and add a call graph for the completion process. This goes a long way in explaining how readline completion works. [stefan]

1.0a4 - 2009-10-27

  • Implement the generator factory using an iterator instead of a list. [stefan]
  • Remove find_completion_word so people don’t get ideas. [stefan]
  • Don’t list distribute as dependency, setuptools will do the right thing. [stefan]

1.0a3 - 2009-10-22

  • Add __slots__ to interface objects to make them immutable. [stefan]
  • Support Python 2.5, 2.6, and 3.1 (thanks to distribute). [stefan]
  • Approach something like test coverage. [stefan]

1.0a2 - 2009-10-08

  • Make the generator factory work for all types of callables. [stefan]
  • Improve examples. [stefan]

1.0a1 - 2009-10-04

  • Initial release.

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