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A pure Python implementation of the Cassowary constraint solving algorithm. Part of the BeeWare suite.

View the Project on GitHub pybee/cassowary


Part of the BeeWare logoBeeWare suite.

A pure Python implementation of the Cassowary constraint-solving algorithm. Cassowary is the algorithm that forms the core of the OS X and iOS visual layout mechanism.


Cassowary is compatible with both Python 2 or Python 3. To install Cassowary in your virtualenv, run:

$ pip install cassowary

Then, in your Python code, you can create and solve constraint systems. See the documentation for examples of what this looks like in practice.


Documentation for Cassowary can be found on Read The Docs.


Cassowary is part of the BeeWare suite. You can talk to the community through:


If you experience problems with Cassowary, you can log them on GitHub. If you want to contribute code, please fork the code and submit a pull request.