Python
Compute distance between sequences. 30+ algorithms, pure python implementation, common interface.

TextDistance

TextDistance -- python library for compare distance between two or more sequences by many algorithms.

Features:

• 30+ algorithms
• Pure python implementation
• Simple usage
• More than two sequences comparing
• Some algorithms have more than one implementation in one class.
• Optional numpy usage for maximum speed.

Algorithms

Edit based

Token based

Sequence based

Compression based

Work in progress. Now all algorithms compare two strings as array of bits, not by chars.

NCD - normalized compression distance.

Functions:

1. bz2_ncd
2. lzma_ncd
3. arith_ncd
4. rle_ncd
5. bwtrle_ncd
6. zlib_ncd

Phonetic

Simple

Installation

Stable:

pip install textdistance

Dev:

pip install -e git+https://github.com/orsinium/textdistance.git#egg=textdistance

Usage

All algorithms have 2 interfaces:

1. Class with algorithm-specific params for customizing.
2. Class instance with default params for quick and simple usage.

All algorithms have some common methods:

1. .distance(*sequences) -- calculate distance between sequences.
2. .similarity(*sequences) -- calculate similarity for sequences.
3. .maximum(*sequences) -- maximum possible value for distance and similarity. For any sequence: distance + similarity == maximum.
4. .normalized_distance(*sequences) -- normalized distance between sequences. The return value is a float between 0 and 1, where 0 means equal, and 1 totally different.
5. .normalized_similarity(*sequences) -- normalized similarity for sequences. The return value is a float between 0 and 1, where 0 means totally different, and 1 equal.

Most common init arguments:

1. qval -- q-value for split sequences into q-grams. Possible values:
   • 1 (default) -- compare sequences by chars.
   • 2 or more -- transform sequences to q-grams.
   • None -- split sequences by words.
2. as_set -- for token-based algorithms:
   • True -- t and ttt is equal.
   • False (default) -- t and ttt is different.

Example

For example, Hamming distance:

import textdistance

textdistance.hamming('test', 'text')
# 1

textdistance.hamming.distance('test', 'text')
# 1

textdistance.hamming.similarity('test', 'text')
# 3

textdistance.hamming.normalized_distance('test', 'text')
# 0.25

textdistance.hamming.normalized_similarity('test', 'text')
# 0.75

textdistance.Hamming(qval=2).distance('test', 'text')
# 2

Any other algorithms have same interface.