tr.index(substring) 和 str.rindex(substring) 

也分别返回子字符串的最低和最高索引。如果字符串中不存在子字符串，则会引发 ValueError

string = "programming"
# index() and rindex() examples
print(string.index('m'))
print(string.index('pro'))
print(string.rindex('m'))
print(string.rindex('game'))

Output:

6
0
7
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
~\AppData\Local\Temp/ipykernel_11336/3954098241.py in 
     11 print(string.index('pro'))  # Output: 0
     12 print(string.rindex('m'))  # Output: 7
---> 13 print(string.rindex('game'))  # Output: ValueError: substring not found
ValueError: substring not found