python 取出字串中的所有词

import os
def fun(data, block, dic, user_dic):
    n = len(data)
    for i in range(n):
        for size in range(block, 1, -1):  # 从最长的块开始，直到长度为2
            if i + size <= n:
                same_word = data[i:i+size]
                if same_word in dic:
                    user_dic.add(same_word)
                    

if __name__ == "__main__":
    ss = set(['天安门','我爱','天安'])
    block = max(len(word) for word in ss)
    a = '我爱北京天安门,天安门上太阳升'
    user_dic = set()
    fun(a, block, ss, user_dic)
    print(user_dic)