Python | Check if substring present in string

Lets solve this general problem of finding if a particular piece of string is present in a larger string in different ways. This is a very common kind of problem every programmer comes across aleast once in his/her lifetime. This article gives various techniques to solve it.

Method 1 : Using in operator
The in operator is the most generic, fastest method to check for a substring, the power of in operator in python is very well known and is used in many operations across the entire language.

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# Python 3 code to demonstrate 
# checking substring in string
# using in operator
  
# initializing string 
test_str = "GeeksforGeeks"
  
# using in to test
# for substring
print ("Does for exists in GeeksforGeeks ? : ")
if "for" in test_str :
    print ("Yes, String found")
else : 
    print ("No, String not found")

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Output :


        
          
          
          
        

            

Does for exists in GeeksforGeeks ? : 
Yes, String found





Method 2 : Using str.find()

str.find() method is generally used to get the lowest index at which the string occurs, but also returns -1, if string is not present, hence if any value returns >= 0, string is present, else not present.













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# Python 3 code to demonstrate  


# checking substring in string 


# using str.find() 


  


# initializing string  


test_str = "GeeksforGeeks"


  


# using str.find() to test 


# for substring 


res = test_str.find("for") 


if res >= 0: 


    print ("for is present in GeeksforGeeks") 


else : 


    print ("for is not present in GeeksforGeeks") 



















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Output :


for is present in GeeksforGeeks





Method 3 : Using str.index() 

This method can be used to performs the similar task, but like str.find(), it doesn’t return a value, but a ValueError if string is not present, hence catching the exception is the way to check for string in substring.













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# Python 3 code to demonstrate  


# checking substring in string 


# using str.index() 


  


# initializing string  


test_str = "GeeksforGeeks"


  


# using str.index() to test 


# for substring 


try :  


    res = test_str.index("forg") 


    print ("forg exists in GeeksforGeeks") 


except : 


    print ("forg does not exists in GeeksforGeeks") 



















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Output :


forg does not exists in GeeksforGeeks





Method 4 : Using operator.contains()

This is lesser known method to check for substring in a string, this method is also effective in accomplishing this task of checking a string in a string.













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# Python 3 code to demonstrate  


# checking substring in string 


# using operator.contains() 


import operator 


  


# initializing string  


test_str = "GeeksforGeeks"


  


# using operator.contains() to test 


# for substring 


if operator.contains(test_str, "for"): 


    print ("for is present in GeeksforGeeks") 


else : 


    print ("for is not present in GeeksforGeeks") 



















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Output :


for is present in GeeksforGeeks




          
          
          
          

            

    

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