Find the similarity metric between two strings

Question

How do I get the probability of a string being similar to another string in Python?

I want to get a decimal value like 0.9 (meaning 90%) etc. Preferably with standar

Answer 1

The builtin SequenceMatcher is very slow on large input, here's how it can be done with diff-match-patch:

from diff_match_patch import diff_match_patch

def compute_similarity_and_diff(text1, text2):
    dmp = diff_match_patch()
    dmp.Diff_Timeout = 0.0
    diff = dmp.diff_main(text1, text2, False)

    # similarity
    common_text = sum([len(txt) for op, txt in diff if op == 0])
    text_length = max(len(text1), len(text2))
    sim = common_text / text_length

    return sim, diff