index() method in Python Lists can be used to find the first occurrence of a given element in the given list.

The index() method by default, returns an integer, denoting the first occurrence of the given element.

Please note that, integer is returned as per 0 based indexing.

Syntax

list.index(item)

item: element whose index is required.

l = [1, 3, 5, 2, 8, 3]
print(l.index(2)) # returns 3
print(l.index(8)) # returns 4
print(l.index(3)) # returns 1 ignoring the further occurrences

O/P

3
4
1

If we try to find the index of the element which does not exists in the given list, then, we get

ValueError : item is not in list

Let’s modify the above code (a bit)

l = [1, 3, 5, 2, 8, 3]
print(l.index(10))

O/P

Traceback (most recent call last):
File “”, line 2, in
ValueError: 10 is not in list

That’s all here.