Leetcode: Substring with Concatenation of All Words @Python

class Solution:
    # @param S, a string
    # @param L, a list of string
    # @return a list of integer
    def findSubstring(self, S, L):
        n,m,w=len(S),len(L),len(L[0])
        rst=[]
        for index in xrange(n-m*w+1):
            seg=[S[i:i+w] for i in xrange(index,index+m*w,w)]
            for item in L:
                if item in seg:
                    seg.remove(item)
                else:
                    break
            if seg==[]:rst.append(index)
        return rst