gistfile1.txt

class Solution(object):
    def strStr(self, source, target):
        if source == None or target == None:
            return -1
        len_t = len(target)
        if len_t == 0:
            return 0
        pos_s = 0
        for char_s in source[:-len_t]:
            pos_t = 0
            for char_t in target:
                if char_t != source[pos_s + pos_t]:
                    break
                pos_t = pos_t + 1
            if pos_t == len_t:
                return pos_s
            pos_s = pos_s + 1
        return -1

a = Solution()
print a.strStr('abc', 'abc')
print a.strStr('abc', 'bc')