Finding a string multiple times in another String - Python

Question

I\'m trying to see if a string exists in another string with out using Python\'s predefined functions such as find and index..

Right now what my function takes 2 strings

Answer 1

Another alternative using regex:

>>> import re
>>> haystack = "abcdefabc. asdli! ndsf acba saa abe?"
>>> needle = "abc"
>>> [m.start() for m in re.finditer(r'{}'.format(re.escape(needle)), haystack)]
[0, 6]

The above solution will not work for overlapping sub-strings, like there are 3 'aa' in 'aaaa'. So, if you want to find overlapping matches as well, then:

>>> haystack = "bobob"
>>> needle = "bob"
>>> [m.start() for m in re.finditer(r'(?={})'.format(re.escape(needle)), haystack)]
[0, 2]