pybktreespellchecker

Python implementation of BK-tree and Levenshtein distance to perform spell checking


Keywords
algorithms, bk-tree, python
License
MIT
Install
pip install pybktreespellchecker==0.0.5

Documentation

pybktree-spell-checker

Implementation of BK-tree and Levenshtein distance to perform spell checking. More details about used algorithms:

This library allows you to enter incorrect/misspelled word and perform dictionary search for similar words using some distance function (Levenshtein by default).

Performance of algorithms

There two ways how single word search and addition to tree can be performed:

  • Using recursion functions
  • Not using recursion functions

Too test performance of both functions types I used dictionary of 466544 words. Test single word search unique words where used to see performance without memoization technique.

Function type Seconds
Recursion load dictionary ±450
Recursion single search ±4.4
Not recursion load dictionary ±450
Not recursion search ±4

Results shows that full dictionary loading time is equal using both functions. While single word search os performed better using not recursion function. All experiments were made on my MacBook Air.

For quicker search memoization optimization technique is used.

Installation

Two ways to install:

  • Clone repo and execute
pip install .
  • Pip install
pip install pybktreespellchecker

Usage

By default distance between two words is calculated using Levenshtein distance algorithm. While creating new BKTree instance you can set new distance function. Functionmust accept two parameters and return integer value of those words distance.

from pybktreespellchecker import BKTree
bkt = BKTree() # instance without dictionary and Levenshtein distance function
bkt = BKTree(words=['one', 'two', 'three']) # instance with dictionary and Levenshtein distance function

# custom words distance function
def length_distance(w1, w2):
    return abs(len(w1) - len(w2))
    
bkt = BKTree(words=['one', 'two', 'three'], distance_func=length_distance) # instance with custom distance function and dictionary

bkt = BKTree.from_file('words.txt') # instance with dictionary whitch is loaded from file

After you created BKTree instance you can add words to tree using function add_word.

bkt.add_word('hello')

Similar word search in BKTree is performed using method search. As a result method returns list of tuples, where first element is distance between words and second element is Node object. Results are sorted by distance value.

result = bkt.search('basketbal', 2)
for i in result:
    print(i[0], i[1].word)

If you want to use only Levenshtein distance function.

from pybktreespellchecker import levenshtein_distance
print(levenshtein_distance('kitten', 'sitting'))
print(levenshtein_distance.ratio)
print(levenshtein_distance.distance_matrix)