Python has a keyword 'in' for finding if a string is a substring of another string. For example
print('ello' in 'hello world')
If you also need the first index of the substring, you can use find(substr) to find the index. If this method returns -1, it means that substring doesn't exist in the string. For example,
Checking if ‘no’ is contained in the string ‘Harry Potter: The Goblet of Fire'
print("Harry Potter: The Goblet of Fire".find('no'))