fastest way to find if string contains substring in python code example

Example 1: how to check for a substring in python

def find_string(string,sub_string):
	return string.find(sub_string)
#.find() also accounts for multiple occurence of the substring in the given string

Example 2: python check if string contains substring

string = "My favourite programming language is Python"
substring = "Python"

if substring in string:
    print("Python is my favorite language")
elif substring not in string:
    print("Python is not my favourite language")