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Describing statistical models in Python using symbolic formulas


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Notice: patsy is no longer under active development. As of August 2021, Matthew Wardrop (@matthewwardrop) and Tomás Capretto (@tomicapretto) have taken on responsibility from Nathaniel Smith (@njsmith) for keeping the lights on, but no new feature development is planned. The spiritual successor of this project is Formulaic, and we recommend that users migrate when possible. For the time being, until major software packages have successfully transitioned, we will attempt to keep patsy working in its current state with current releases in the Python ecosystem.

Patsy is a Python library for describing statistical models (especially linear models, or models that have a linear component) and building design matrices. Patsy brings the convenience of R "formulas" to Python.

PyPI - Version PyPI - Python Version PyPI - Status


  • Python (2.6, 2.7, or 3.3+)
  • six
  • numpy
  • Optional:
    • pytest/pytest-cov: needed to run tests
    • scipy: needed for spline-related functions like bs


pip install patsy (or, for traditionalists: python install)


2-clause BSD, see LICENSE.txt for details.