Maybe

A simple Maybe (Option) type for Python 3 inspired by Rust, fully type annotated.

Installation

Latest release:

pip install rustedpy-maybe

Latest GitHub master branch version:

pip install git+https://github.com/rustedpy/maybe

There are no dependencies outside of the Python standard library. However, if you wish to use the Result conversion methods (see examples in the next section), you will need to install the result extra.

In this case, rather than installing via one of the commands above, you can install the package with the result extra either from the latest release:

pip install rustedpy-maybe[result]

or from the GitHub master branch:

pip install git+https://github.com/rustedpy/maybe[result]

Summary

Experimental. API subject to change.

The idea is that a possible value can be either Some(value) or Nothing(), with a way to differentiate between the two. Some and Nothing are both classes encapsulating a possible value.

Example usage:

from maybe import Nothing, Some

o = Some('yay')
n = Nothing()
assert o.unwrap_or_else(str.upper) == 'yay'
assert n.unwrap_or_else(lambda: 'default') == 'default'

There are some methods that support conversion from a Maybe to a Result type in the result library. If you wish to leverage these methods, you must install the result extra as described in the installation section.

Example usage:

from maybe import Nothing, Some
from result import Ok, Err

o = Some('yay')
n = Nothing()
assert o.ok_or('error') == Ok('yay')
assert o.ok_or_else(lambda: 'error') == Ok('yay')
assert n.ok_or('error') == Err('error')
assert n.ok_or_else(lambda: 'error') == Err('error')

Contributing

These steps should work on any Unix-based system (Linux, macOS, etc) with Python and make installed. On Windows, you will need to refer to the Python documentation (linked below) and reference the Makefile for commands to run from the non-unix shell you're using on Windows.

1. Setup and activate a virtual environment. See Python docs for more information about virtual environments and setup.
2. Run make install to install dependencies
3. Switch to a new git branch and make your changes
4. Test your changes:
   • make test
   • make lint
   • You can also start a Python REPL and import maybe
5. Update documentation
   • Edit any relevant docstrings, markdown files
   • Run make docs
6. Add an entry to the changelog
7. Git commit all your changes and create a new PR.

License

MIT License