cmd2 - Feature-Rich Interactive Command Line Applications

3.4.0 · active · verified Sat Apr 11

cmd2 is a powerful Python library for quickly building feature-rich and user-friendly interactive command-line applications. It extends Python's built-in `cmd` module, providing a comprehensive set of enhancements including robust tab completion, searchable command history, text and Python scripting, and advanced argument parsing with `argparse`. The library is actively maintained with a frequent release cadence, continuously improving its capabilities and user experience.

Warnings

breaking Major breaking changes occurred in `cmd2` version 3.x (from 2.x). Key changes include a new dependency on `prompt-toolkit` (replacing all `readline` usage) and `rich` for formatting. The Transcript Testing feature was removed, and `completer` and `choices_provider` functions now return `cmd2.Completions` and `cmd2.Choices` objects instead of lists of strings.
Fix: Review the official 'Migration Guide' for upgrading from 2.x to 3.x in the cmd2 documentation. Adapt custom completer/choices_provider functions to return the new object types.
breaking `cmd2` dropped support for Python 3.8 in version 2.6.0, and Python 3.5 support ended in version 2.0.0. Current versions require Python 3.10+.
Fix: Ensure your project uses Python 3.10 or higher to be compatible with current `cmd2` versions.
breaking The `Cmd.cmdqueue` attribute, which was used in Python's built-in `cmd` module for queued input lines, was removed in `cmd2` version 0.9.13.
Fix: Avoid using `Cmd.cmdqueue`. `cmd2` provides alternative mechanisms for running commands via `cmdloop()`, text scripts, Python scripts, and history replays, which offer more consistent behavior.
gotcha Unlike Python's standard `cmd` module, `cmd2` completely ignores empty lines entered at the prompt by default. The `cmd.emptyline()` method (which, by default, repeats the last command) is never called in `cmd2`.
Fix: If you require custom behavior for empty lines, you will need to implement a post-parsing hook or similar mechanism to detect and handle them manually.
deprecated Using `py run('myscript.py')` to execute Python scripts is deprecated. The `pyscript` command is now the recommended method, offering improved features like tab-completion of file system paths and the ability to pass command-line arguments.
Fix: Migrate from `py run()` to the `pyscript` command for executing Python scripts within your `cmd2` application.

Install

pip install cmd2 Install latest stable version

Imports

Cmd
```
from cmd2 import Cmd
```
Statement
```
from cmd2 import Statement
```
Commonly used for type hinting command arguments, especially when not using @with_argparser.

Quickstart

This minimal example demonstrates how to create a basic `cmd2` application by subclassing `cmd2.Cmd` and defining a `do_` method for a command. Running `cmdloop()` starts the interactive shell, and you can type `hello_world` or `quit` to exit.

import cmd2
import sys

class FirstApp(cmd2.Cmd):
    """A simple cmd2 application."""

    def do_hello_world(self, _: cmd2.Statement):
        """Says hello to the world."""
        self.poutput('Hello World')

if __name__ == '__main__':
    c = FirstApp()
    sys.exit(c.cmdloop())

view raw JSON →