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This gist do a fuzzy matching of documents on the basis of levenshtein distance and returns a similarity score. Time and space complexities are O(mn), where m and n are documents length which we match
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import numpy as np | |
from pprint import pprint | |
def levenshtein_distance(pattern, docs, ignore_case=True) -> dict: | |
"""Do a fuzzy matching of documents using levenshtein distance. | |
Parameters | |
---------- | |
pattern : str | |
The document which you want to match | |
docs : list | |
The documents which you want to match with | |
ignore_case : bool, optional | |
Whether the matching is case sensitive or not (default is True) | |
Returns | |
------- | |
dict | |
a dictionary of similarity scores of all documents with pattern in the order passed in docs | |
""" | |
if ignore_case: | |
pattern = pattern.lower() | |
pattern_len = len(pattern) | |
similarity_score = {} | |
count = 1 | |
for doc in docs: | |
if ignore_case: | |
doc = doc.lower() | |
if pattern == doc: | |
similarity_score['doc' + str(count)] = 1.0 | |
count += 1 | |
continue | |
doc_len = len(doc) | |
cache_table = np.empty(shape=(doc_len+1, pattern_len+1)) | |
cache_table[0][0] = 0 | |
space_penalty = 1 | |
for j in range(1, pattern_len+1): | |
cache_table[0][j] = space_penalty*j | |
for i in range(1, doc_len+1): | |
cache_table[i][0] = space_penalty*i | |
for i in range(1, doc_len+1): | |
for j in range(1, pattern_len+1): | |
miss_penalty = cache_table[i-1][j-1] | |
if pattern[j-1] != doc[i-1]: | |
miss_penalty += 1 | |
cache_table[i][j] = min([space_penalty+cache_table[i-1][j], | |
space_penalty+cache_table[i][j-1], | |
miss_penalty]) | |
lev_dist = cache_table[doc_len][pattern_len] | |
similarity_score['doc' + str(count)] = (pattern_len + doc_len - | |
lev_dist) / (pattern_len + doc_len) | |
count += 1 | |
return similarity_score | |
if __name__ == '__main__': | |
pattern = 'this is a test for fuzzy wuzzy match' | |
docs = ['a test for fuzzy match', 'test fuzzy matching', 'this is a test for fuzzy wuzzy match', | |
'this is test for fuzy wuzy match', 'this is a for fuzzy wuzzy match'] | |
similarity_score = levenshtein_distance(pattern, docs) | |
pprint(similarity_score) | |
# output -> | |
# {'doc1': 0.7586206896551724, | |
# 'doc2': 0.5818181818181818, | |
# 'doc3': 1.0, | |
# 'doc4': 0.9411764705882353, | |
# 'doc5': 0.9253731343283582} |
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