Why isn't this code working?

[MckJohan]

its not working because, find() method returns the lowest index of the substring if it is found in given string. If its is not found then it returns -1.

>>> x='012345horwitz678910'
>>> x.find('horwitz')
6
>>> x.find('XXX')
-1
>>> 'horwitz' in x
True
>>>