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.

rl exports these components:

completer

Interface to the readline completer. Used to configure the completion aspects of readline.

completion

Interface to the active readline completion. Used to interact with readline when a completion is in progress.

history

Interface to the readline history. Used to read and write history files and to manipulate history entries.

readline

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.

generator

A decorator turning any callable into a completion entry function that can be handed to readline.

print_exc

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.

For further details please refer to the API Documentation.

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

rl requires Python 2.7 or higher. The installer builds GNU Readline 8.2 and a Python extension module.

On Mac OS X make sure you have Xcode Tools installed. Open a Terminal window and type:

gcc --version

You either see some output (good) or an installer window pops up. Click the "Install" button to install the command line developer tools. A more detailed tutorial is available from the Mac Install Guide.

On Linux and BSD systems you probably already have a C compiler, but you may need to verify the development environment is complete. For example, Ubuntu lacks the Python headers by default and Fedora is missing some compiler configuration. Lastly, readline needs a termcap library to link to.

Ubuntu/Debian:

sudo apt install build-essential
sudo apt install python3-dev
sudo apt install libncurses-dev

Redhat/Fedora:

sudo dnf install gcc
sudo dnf install redhat-rpm-config
sudo dnf install ncurses-devel

Then type:

pip install rl

kmd.Kmd is an rl-enabled version of cmd.Cmd.