Code:
def stringBetween(stringToSearch, startString, endString):
        #stringBetween by Nat + Monarchy for Python 3.1
        initPos = stringToSearch.find(startString)
        if initPos == '-1':
                return ''
        else:
                initPos = initPos + len(startString)
                stringLength = stringToSearch.find(endString, initPos)
        return stringToSearch[initPos:stringLength]
       
#Example usage
x = 'this is my [tag]dog[/tag]'
y = stringBetween(x, "[tag]", "[/tag]")
No idea if anyone will get anything out of this but enjoy.