index()是Python中的内置函数，它从列表的开头搜索给定元素，并返回该元素出现的最低索引。
用法:
list_name.index(element, start, end)
参数：
element - The element whose lowest index will be returned.
start (Optional) - The position from where the search begins.
end (Optional) - The position from where the search ends.
返回值：
Returns lowest index where the element appears.
错误：
If any element which is not present is searched, it returns a ValueError
代码1：
# Python3 program for demonstration
# of list index() method
list1 = [1, 2, 3, 4, 1, 1, 1, 4, 5]
# Will print the index of '4' in list1
print(list1.index(4))
list2 = ['cat', 'bat', 'mat', 'cat', 'pet']
# Will print the index of 'cat' in list2
print(list2.index('cat'))输出：
3 0
代码2：
# Python3 program for demonstration
# of index() method
list1 = [1, 2, 3, 4, 1, 1, 1, 4, 5]
# Will print index of '4' in sublist
# having index from 4 to 8.
print(list1.index(4, 4, 8))
# Will print index of '1' in sublist
# having index from 1 to 7.
print(list1.index(1, 1, 7))
list2 = ['cat', 'bat', 'mat', 'cat',
'get', 'cat', 'sat', 'pet']
# Will print index of 'cat' in sublist
# having index from 2 to 6
print(list2.index('cat', 2, 6 ))输出：
7 4 3
代码3：
# Python3 program for demonstration
# of list index() method
# Random list having sublist and tuple also
list1 = [1, 2, 3, [9, 8, 7], ('cat', 'bat')]
# Will print the index of sublist [9, 8, 7]
print(list1.index([9, 8, 7]))
# Will print the index of tuple
# ('cat', 'bat') inside list
print(list1.index(('cat', 'bat')))输出：
3 4
代码4： ValueError
# Python3 program for demonstration
# of index() method error
list1 = [1, 2, 3, 4, 1, 1, 1, 4, 5]
# Return ValueError
print(list1.index(10))输出：
Traceback (most recent call last):
File "/home/b910d8dcbc0f4f4b61499668654450d2.py", line 8, in
print(list1.index(10))
ValueError:10 is not in list
注：本文由纯净天空筛选整理自Striver大神的英文原创作品 Python list | index()。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。