Question

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Search for string allowing for one mismatch in any location of the string

I am given a string s and a string t. Is there a regular expression to find all occurrences of t inside s with at most one mismatched character. (At most one character from t is allowed to be substituted by another.)

Answer 1

I wouldn’t necessarily do this with regex. You can use Levenshtein distance.

>>> import Levenshtein
>>> s = "spam ham and eggs"
>>> t = "ram"
>>> for i,_ in enumerate(s): 
...   s_ = s[i:i+len(t)]
...   if Levenshtein.distance(s_, t) == 1:
...     print s_
... 
pam
ham