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A naive implementation of C3 linearization algorithm used in Python's MRO

Project description

C3 Linearization Algorithm

c3linear is a naïve implementation of C3 linearization algorithm. It's used in Python 2.3+ for Method Resolution Order. See Raymond Hettinger's Python’s super() considered super! for more information.

About implementation

The recursive implementation can be found at c3linear.mro.mro. It used an auxiliary function _merge as well as a bunch of classes to help with algorithm's readability.

Motivation

The project's come to life as a byproduct of debugging an overcomplicated hierarchy of mixin classes. I thought I knew how exactly MRO is computed, but it turned out I didn't.

I've tried to keep the code idiomatic and easy to follow at the expense of performance. The project is really took a couple of hours to complete. Although I didn't care about time complexity and didn't check correctness as thoroughly as I should, I think the project may help someone who want to learn how Python's Method Resolution Order works.

Usage

Library

  • Get the code and install it with python setup.py install (Python 3.6+ required)
  • Import from c3linear.mro import mro
  • Check against built-in MRO:
>>> class A: pass
>>> class`B(A): pass
>>> mro(B) == B.mro()
True 

Take a look at tests for more examples.

Testing

  • Install dependencies:
pip install -e .
  • (Optional) Install extra packages:
pip install -e .[extra]
  • Run tests with:
python setup.py test
  • Run flake8 for PEP8 compliance testing:
python setup.py flake8
  • Run mypy:
mypy c3linear/

Contributing

If you've found a bug, please open an issue describing the problem first.

Licence

The project is licensed under MIT License. For further information see LINCENSE file.

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