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Snowball stemming library collection for Python

This document pertains to the Python version of the stemmer library distribution, available for download from:

Original program is maintained at following place:

Original Snowball product created by Dr Martin Porter and Richard Boulton (Java porting). Original Snowball and my products are released under BSD license.

How to use library

The snowballstemmer module has two functions.

The snowballstemmer.algorithms function returns a list of avilable algorithm name' string.

The snowballstemmer.stemmer function accepts algorithm name and returns Stemmer objects.

Stemmer objects have Stemmer.stemWord(word) method and Stemmer.stemWords(word[]) method.

import snowballstemmer

stemmer = snowballstemmer.stemmer('english');
print(stemmer.stemWords("We are the world".split()));

Stemmer objects have Stemmer.maxCacheSize property. They cache result within the value. Default is 10000.

Accerarates Stemming

if PyStemmer is installed, snowballstemmer.stemmer returns PyStemmer's Stemmer objects. This Stemmer object has same methods (Stemmer.stemWord(), Stemmer.stemWords()).

PyStemmer is a Snowball's libstemmer_c wrapper module and it returns 100% compatible result with snowballstemmer.

PyStemmer has faster speed because it uses C-lang module, and snowballstemmer has higher usability because it is pure Python module.

Benchmark

Test Case: Snowball stemmer check data (16 algorithms, total 582560 words, cache hit 0%) Computer: MacBook Pro 3rd Gen Corei7 2.3GHz

  • Python 2.7 + snowballstemmer : 2m 30s
  • PyPy 1.9 + snowballstemmer : 45s
  • Python 2.7 + PyStemmer : 5s

This test case is much harder than usual usecases!

The TestApp example

The testapp.py example program allows you to run any of the stemmers on a sample vocabulary.

Usage:

testapp.py <algorithm> "sentences ... "

$ python testapp.py English "sentences... "

Thanks

  • Original Snowball authors
  • Emil Stenström

License

It is a BSD licensed library.

Copyright (c) 2013, Yoshiki Shibukawa

All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  • Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
  • Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.