I'm writing a little function to return the index of the first occurrence of a string in a list of strings, using a "fuzzy" comparison.

My question is: what is the proper way to signify the target string not matching any in the source list? 

The obvious (only?) thing to do is to return -1. But since -1 in Python means the last element of a sequence, it occurs to me this may not be good Python style. Is there a more Pythonic (Pythonesque?) way?