python中index()與find()的差異

發現了python中的index()和find()實現的功能相似，去百度發現還是有不一樣的。

先來個正常的　

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

輸出結果為：

0
0

Process finished with exit code 0

繼續

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

輸出結果為：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，下面來找下index的語法使用：

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()相當於find()，但是在沒有找到子串的時候會有報錯，影響程序執行。

再來看看find的語法使用：

def find(self, sub, start=None, 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時不會拋出異常，而是會返回-1，因此不會影響程序的執行。