Finding last index of a substring in a string

Question

So I'm looking for a way to find the last index of a substring in a string. Here's some pseudo-code.

string = "hello 123 this is a test"
substring = "123 this"

>>> string.find_substring_index(substring)
13

"hello 123 this is a test"
#             ^

Any built-in function to do this? Or do I have to manually "match" the string and return the last occurrence?

Answer 1

Add the length of the substring to the index of the substring.

def find_substring_index(string, substring):
    return string.index(substring) + len(substring) - 1

Subtract 1 because you want the index of the last character, otherwise it will return the index just past the match.