The syntax for the index () method is given as follows:

list.index(item)

The index () method is used to find the index of a particular item in a list. For example, consider the following code snippet:

>>> OS = ['kali', 'Ubuntu', 'debian', 'RHEL', 'Centos']

>>> OS.index("debian")

2

>>> OS.index("mint")


Traceback (most recent call last):

  File "<pyshell#55>", line 1, in <module>

    OS.index("mint")

ValueError: 'mint' is not in list

>>> 

From the preceding example, you can easily understand that if a list does not contain the item, then the index () method shows ValueError.

Let's see another example:

>>> OS = ['kali', 'Ubuntu', 'debian', 'RHEL', 'Centos','RHEL']

>>> OS.index("RHEL")

3

>>> 

If an item occurs two times, then the index method returns the index of the first occurrence.

Consider a list of avengers [‘iron-man', 'hulk', 'Thor']. As we know, one name is missing: 'Captain-America', and I want to insert 'Captain-America' in the first index. To do this, we can use the insert () method.