w3resource

Python: Find the longest common sub-string from two given strings

Python String: Exercise-69 with Solution

Write a Python program to find the longest common sub-string from two given strings.

Sample Solution:-

Python Code:

from difflib import SequenceMatcher 
  
def longest_Substring(s1,s2): 
  
     seq_match = SequenceMatcher(None,s1,s2) 
  
     match = seq_match.find_longest_match(0, len(s1), 0, len(s2)) 
  
     # return the longest substring 
     if (match.size!=0): 
          return (s1[match.a: match.a + match.size])  
     else: 
          return ('Longest common sub-string not present')  

s1 = 'abcdefgh'
s2 = 'xswerabcdwd'
print("Original Substrings:\n",s1+"\n",s2)
print("\nCommon longest sub_string:")
print(longest_Substring(s1,s2))

Sample Output:

Original Substrings:
 abcdefgh
 xswerabcdwd

Common longest sub_string:
abcd
Original Substrings:
 abcdefgh
 xswerabcdwd

Common longest sub_string:
abcd

Pictorial Presentation:

Python String:  Find the longest common sub-string from two given strings.

Flowchart:

Flowchart: Find the longest common sub-string from two given strings

Python Code Editor:

Have another way to solve this solution? Contribute your code (and comments) through Disqus.

Previous: Write a Python program to create two strings from a given string. Create the first string using those character which occurs only once and create the second string which consists of multi-time occurring characters in the said string.
Next: Write a Python program to create a string from two given strings concatenating uncommon characters of the said strings.

What is the difficulty level of this exercise?

Test your Programming skills with w3resource's quiz.



Python: Tips of the Day

Check if a given key already exists in a dictionary:

In is the intended way to test for the existence of a key in a dict.

d = {"key1": 10, "key2": 23}

if "key1" in d:
    print("this will execute")

if "nonexistent key" in d:
    print("this will not")

If you wanted a default, you can always use dict.get():

d = dict()

for i in range(100):
    key = i % 10
    d[key] = d.get(key, 0) + 1

and if you wanted to always ensure a default value for any key you can either use dict.setdefault() repeatedly or defaultdict from the collections module, like so:

from collections import defaultdict

d = defaultdict(int)

for i in range(100):
    d[i % 10] += 1

but in general, the in keyword is the best way to do it.

Ref: https://bit.ly/2XPMRyz