python中index()与find()的差异

发现了python中的index()和find()实现的功能相似，去百度发现还是有不一样的。

先来个正常的　

msg = "mynameishelie"
print(msg.index("m"))
print(msg.find("m"))

输出结果为：

0
0

Process finished with exit code 0

继续

msg = "mynameishelie"
print(msg.index("L"))
print(msg.find("L"))

输出结果为：提示 substring not found

Traceback (most recent call last):
File "C:/Users/PycharmProjects/python/index_find.py",line 28,in <module>
print(msg.index("L"))
ValueError: substring not found

Process finished with exit code 1

好了，下面来找下index的语法使用：

def index(self,sub,start=None,end=None):

# Like S.find() but raise ValueError when the substring is not found.
可以看出index()相当于find()，但是在没有找到子串的时候会有报错，影响程序执行。

再来看看find的语法使用：

def find(self,end=None):

# Return the lowest index in S where substring sub is found,# such that sub is contained within S[start:end].  Optional# arguments start and end are interpreted as in slice notation.# Return -1 on failure.和index()不同的是find()在找不到substring时不会抛出异常，而是会返回-1，因此不会影响程序的执行。