How to Check if a String contains a Substring in Python?

A substring is a sequence of characters within a String. The following are the methods in Python to check if a string contains another string i.e. substring.

By using find() method
By using in operator
By using count() method
By using str.index() method
By using operator.contains() method

Method 1: By using find() method

The method find() checks whether a string contains a particular substring or not. If the string contains that particular substring, the method returns the starting index of the substring else it returns -1.

Syntax: string.find(substring)

Example: Checking for the presence of substring within the string using find() method

str="Safa Mulani is a student of Engineering discipline." 
sub1="Safa" 
sub2="Engineering" 

print(str.find(substring1)) 

print(str.find(substring2))

Output:

0
28

Method 2: By using in operator

The in operator checks for the presence of substring within a string, if the substring is present it returns TRUE else it returns FALSE.

Syntax: substring in string_object

Example: Checking for the presence of substring within the string using in operator

str="Safa Mulani is a student of Engineering discipline." 
sub1="Safa" 
sub2="Done" 

print(sub1 in str) 

print(sub2 in str)

Output:

True
False

Method 3: By using count() method

The count() method checks for the occurrence of substring in a string. If the substring is not found in the string, it returns 0.

Syntax: string.count(substring)

Example: Checking for the presence of substring within a string using count() method

str="Safa Mulani is a student of Engineering discipline." 
sub1="Safa" 
sub2="student" 
sub3="Done"
print(str.count(sub1)) 

print(str.count(sub2))

print(str.count(sub3))

Output:

1
1
0

Method 4: By using index() method

The method checks for the presence of a substring in a string. If the substring is not present in the string then it doesn’t return any value, rather it generates a ValueError.

Syntax: string.index(substring)

Example: Checking for the presence of a substring in a string using the index() method

str = "Safa is a Student."
try :  
    result = str.index("Safa") 
    print ("Safa is present in the string.") 
except : 
    print ("Safa is not present in the string.")

Output:

Safa is present in the string.

Method 5: By using the operator.contains() method

Syntax: operator.contains(string,substring)

Example: Checking for the presence of a substring in the string using the operator.contains() method

import operator 
  
str = "Safa is a Student."
  
if operator.contains(str, "Student"): 
    print ("Student is present in the string.") 
else : 
    print ("Student is not present in the string.")

Output: Student is present in the string.

References

Python String