Some platforms, such as Mac OS X, do not ship with GNU readline installed. The readline extension module in the standard library of Mac "system" Python uses NetBSD's editline (libedit) library instead, which is a readline replacement with a less restrictive software license.
As the alternatives to GNU readline do not have fully equivalent functionality, it is useful to add proper readline support to these platforms. This module achieves this by bundling the standard Python readline module with the GNU readline source code, which is compiled and statically linked to it. The end result is a package which is simple to install and requires no extra shared libraries.
The module can be used with both Python 2.x and 3.x, and has been tested with Python versions 2.5, 2.6, 2.7 and 3.1. The major and minor numbers of the module version reflect the version of the underlying GNU readline library, while the third (patch) number distinguishes different module updates based on the same readline library.
This module is usually unnecessary on Linux and other Unix systems with default readline support. An exception is if you have a Python distribution that does not include GNU readline due to licensing restrictions (such as ActiveState's ActivePython). If you are using Windows, which also ships without GNU readline, you might want to consider using the pyreadline module instead, which is a readline replacement written in pure Python that interacts with the Windows clipboard.
The latest development version is available from the GitHub repository.