Python: Check if String Contains Substring

In this article, we’ll examine four ways to use Python to check whether a string contains a substring. Each has their own use-cases and pros/cons, some of which we’ll briefly cover here:

1) The in Operator

The easiest way to check if a Python string contains a substring is to use the in operator. The in operator is used to check data structures for membership in Python. It returns a Boolean (either True or False) and can be used as follows:

fullstring = "StackAbuse"
substring = "tack"

if substring in fullstring:
    print "Found!"
else:
    print "Not found!"

This operator is shorthand for calling an object’s __contains__ method, and also works well for checking if an item exists in a list.

2) The String.index() Method

The String type in Python has a method called index that can be used to find the starting index of the first occurrence of a substring in a string. If the substring is not found, a ValueError exception is thrown, which can to be handled with a try-except-else block:

fullstring = "StackAbuse"
substring = "tack"

try:
    fullstring.index(substring)
except ValueError:
    print "Not found!"
else:
    print "Found!"

This method is useful

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