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NAME
jellyfish - jellyfish Documentation
OVERVIEW
jellyfish is a library of functions for approximate and phonetic matching of strings.
The library provides implementations of the following algorithms:
Phonetic Encoding
These algorithms convert a string to a normalized phonetic encoding, converting a word to a
representation of its pronunciation. Each takes a single string and returns a coded representation.
American Soundex
soundex(s)
Calculate the American Soundex of the string s.
Soundex is an algorithm to convert a word (typically a name) to a four digit code in the form 'A123'
where 'A' is the first letter of the name and the digits represent similar sounds.
For example soundex('Ann') == soundex('Anne') == 'A500' and soundex('Rupert') == soundex('Robert') ==
'R163'.
See the Soundex article at Wikipedia for more details.
Metaphone
metaphone(s)
Calculate the metaphone code for the string s.
The metaphone algorithm was designed as an improvement on Soundex. It transforms a word into a string
consisting of '0BFHJKLMNPRSTWXY' where '0' is pronounced 'th' and 'X' is a '[sc]h' sound.
For example metaphone('Klumpz') == metaphone('Clumps') == 'KLMPS'.
See the Metaphone article at Wikipedia for more details.
NYSIIS
nysiis(s)
Calculate the NYSIIS code for the string s.
The NYSIIS algorithm is an algorithm developed by the New York State Identification and Intelligence
System. It transforms a word into a phonetic code. Like soundex and metaphone it is primarily intended
for use on names (as they would be pronounced in English).
For example nysiis('John') == nysiis('Jan') == JAN.
See the NYSIIS article at Wikipedia for more details.
Match Rating Approach (codex)
match_rating_codex(s)
Calculate the match rating approach value (also called PNI) for the string s.
The Match rating approach algorithm is an algorithm for determining whether or not two names are
pronounced similarly. The algorithm consists of an encoding function (similar to soundex or nysiis)
which is implemented here as well as match_rating_comparison() which does the actual comparison.
See the Match Rating Approach article at Wikipedia for more details.
Stemming
Porter Stemmer
porter_stem(s)
Reduce the string s to its stem using the common Porter stemmer.
Stemming is the process of reducing a word to its root form, for example 'stemmed' to 'stem'.
Martin Porter's algorithm is a common algorithm used for stemming that works for many purposes.
See the official homepage for the Porter Stemming Algorithm for more details.
String Comparison
These methods are all measures of the difference (aka edit distance) between two strings.
Levenshtein Distance
levenshtein_distance(s1, s2)
Compute the Levenshtein distance between s1 and s2.
Levenshtein distance represents the number of insertions, deletions, and subsititutions required to
change one word to another.
For example: levenshtein_distance('berne', 'born') == 2 representing the transformation of the first e to
o and the deletion of the second e.
See the Levenshtein distance article at Wikipedia for more details.
Damerau-Levenshtein Distance
damerau_levenshtein_distance(s1, s2)
Compute the Damerau-Levenshtein distance between s1 and s2.
A modification of Levenshtein distance, Damerau-Levenshtein distance counts transpositions (such as ifhs
for fish) as a single edit.
Where levenshtein_distance('fish', 'ifsh') == 2 as it would require a deletion and an insertion, though
damerau_levenshtein_distance('fish', 'ifsh') == 1 as this counts as a transposition.
See the Damerau-Levenshtein distance article at Wikipedia for more details.
Hamming Distance
hamming_distance(s1, s2)
Compute the Hamming distance between s1 and s2.
Hamming distance is the measure of the number of characters that differ between two strings.
Typically Hamming distance is undefined when strings are of different length, but this implementation
considers extra characters as differing. For example hamming_distance('abc', 'abcd') == 1.
See the Hamming distance article at Wikipedia for more details.
Jaro Distance
jaro_distance(s1, s2)
Compute the Jaro distance between s1 and s2.
Jaro distance is a string-edit distance that gives a floating point response in [0,1] where 0 represents
two completely dissimilar strings and 1 represents identical strings.
Jaro-Winkler Distance
jaro_winkler(s1, s2)
Compute the Jaro-Winkler distance between s1 and s2.
Jaro-Winkler is a modification/improvement to Jaro distance, like Jaro it gives a floating point response
in [0,1] where 0 represents two completely dissimilar strings and 1 represents identical strings.
See the Jaro-Winkler distance article at Wikipedia for more details.
Match Rating Approach (comparison)
match_rating_comparison(s1, s2)
Compare s1 and s2 using the match rating approach algorithm, returns True if strings are
considered equivalent or False if not. Can also return None if s1 and s2 are not comparable
(length differs by more than 3).
The Match rating approach algorithm is an algorithm for determining whether or not two names are
pronounced similarly. Strings are first encoded using match_rating_codex() then compared according to
the MRA algorithm.
See the Match Rating Approach article at Wikipedia for more details.
Changelog
0.5.6 - June 23 2016
• bugfix for metaphone & soundex raising unexpected TypeErrors on Windows (#54)
0.5.5 - June 21 2016
• bugfix for metaphone WH case
0.5.4 - May 13 2016
• bugfix for C version of damerau_levenshtein thanks to Tyler Sellon
0.5.3 - March 15 2016
• style/packaging changes
0.5.2 - February 3 2016
• testing fixes for Python 3.5
• bugfix for Metaphone w/ silent H thanks to Jeremy Carbaugh
0.5.1 - July 12 2015
• bugfixes for NYSIIS
• bugfixes for metaphone
• bugfix for C version of jaro_winkler
0.5.0 - April 23 2015
• consistent unicode behavior, all functions take unicode and reject bytes on Py2 and 3, C and Python
• parametrize tests
• Windows compiler support
0.4.0 - March 27 2015
• tons of new tests
• documentation
• split out cjellyfish
• test all w/ unicode and plenty of fixes to accommodate
• 100% test coverage
0.3.4 - February 4 2015
• fix segfaults and memory leaks via Danrich Parrol
0.3.3 - November 20 2014
• fix bugs in damerau and NYSIIS
0.3.2 - August 11 2014
• fix for jaro-winkler from David McKean
• more packaging fixes
0.3.1 - July 16 2014
• packaging fix for C/Python alternative
0.3.0 - July 15 2014
• python alternatives where C isn't available
0.2.2 - March 14 2014
• testing fixes
• assorted bugfixes in NYSIIS
0.2.0 - January 26 2012
• incorporate some speed changes from Peter Scott
• segfault bugfixes.
0.1.2 - September 16 2010
• initial working release
IMPLEMENTATION
Each algorithm has C and Python implementations.
On a typical CPython install the C implementation will be used. The Python versions are available for
PyPy and systems where compiling the CPython extension is not possible.
• genindex
• modindex
• search
AUTHOR
James Turk
COPYRIGHT
2017, James Turk