如果找不到目标元素，index会报错，find会返回-1
>>> s="hello world" >>> s.find("llo") 2 >>> s.index("llo") 2 >>> s.index("llos") Traceback (most recent call last): File "<stdin>", line 1, in <module> ValueError: substring not found >>> s.find("llos") -1 >>>
参考：
https://blog.csdn.net/yolandera/article/details/80264876
原文：https://www.cnblogs.com/sea-stream/p/11273317.html