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Pure-Python implementations of the Snowball stemmers

Project Description

The traditional way of using the Snowball stemmers in Python is via the pystemmer package, which provides a Python wrapper around the Snowball C library. However, Python C extensions are problematic in some environments. Therefore, this package provides pure-Python implementations of the Snowball stemming algorithms.

The implementations of the stemming algorithms is translated from the Snowball language to Python via sbl2py.


Installing purestemmer is easy using pip:

pip install purestemmer


Usually, you’ll prefer to use the pystemmer module whenever that is possible, because it’s much faster than purestemmer:

    import Stemmer
except ImportError:
    # pystemmer is not available, use purestemmer instead
    import purestemmer as Stemmer

Since purestemmer has the same public API and provides the same algorithms as pystemmer, there should be no need to change any code when switching between pystemmer and purestemmer like this.

Please see the pystemmer documentation for details on how to use the stemming algorithms.

Differences between purestemmer and pystemmer

  • purestemmer has only been tested on Python 2.7
  • purestemmer.Stemmer instances are thread-safe
  • purestemmer is on average about 100x slower than pystemmer


purestemmer itself is covered by the MIT License. The underlying Snowball algorithms are covered by the BSD-3 License. Please see the LICENSE file for details.

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