1：python限定参数类型为list报错name List is not defined
A：from typing import List
https://bbs.csdn.net/topics/392765076
2:python3中str和list互转
A:str="".join(list) list=list(str)
https://www.cnblogs.com/sench/p/8718008.html
3:python3中字符串的截取
A：str1=str[x:y]，x和y可以是负值，如果不传入冒号表示是第几个字符
https://www.cnblogs.com/xunbu7/p/8074417.html
4:python3中list的合并
A：listA+listB 或者extend()
https://blog.csdn.net/sdu_hao/article/details/83037940
