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SequenceMatcher in Python for Longest Common Substring.
Given two strings, our task is to print the longest common sub-string. We will solve problem in python using SequenceMatcher.find_longest_match () method.
Class difflib.SequenceMatcher is a flexible class for comparing pairs of sequences of any type, so long as the sequence elements are hashable.
find_longest_match(a, x, b, y)
Find longest matching block in a[a:x] and b[b:y].
Examples
Input: str1 = "pythonprogramming",
str2 = "pro"
Output: pro
Algorithm
Step 1: Enter two string. Step 2: initialize SequenceMatcher object with the input string. Step 3: find the match of longest sub-string output. Step 4: print longest substring.
Example Code
# Python program to find Longest Common Sub-string
from difflib import SequenceMatcher
def matchsubstring(m,n):
seqMatch = SequenceMatcher(None,m,n)
match = seqMatch.find_longest_match(0, len(m), 0, len(n))
if (match.size!=0):
print ("Common Substring ::>",m[match.a: match.a + match.size])
else:
print ('No longest common sub-string found')
# Driver program
if __name__ == "__main__":
X = input("Enter first String ")
Y = input("Enter second String ")
matchsubstring(X,Y)
Output
Enter first String pythonprogramming Enter second String pro Common Substring ::> pro
Updated on: 30-Jul-2019
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