index() is an inbuilt function in Python, which searches for a given element from the start of the list and returns the lowest index where the element appears. 
Syntax : 
 

list_name.index(element, start, end)

Parameters : 
 

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.

Returns : 
 

Returns lowest index where the element appears.

Error : 
 

If any element which is not present is searched,
it returns a ValueError

Code #1 : 
 

Output : 
 

3
0

  
Code #2 : 
 

Output : 
 

7
4
3

 
Code #3 : 
 

Output : 
 

3
4

  
Code #4 : ValueError 
 

Output : 
 

Traceback (most recent call last):
  File "/home/b910d8dcbc0f4f4b61499668654450d2.py", line 8, in 
    print(list1.index(10))
ValueError: 10 is not in list

Code #5 : When 2 arguments are passed

When two arguments are passed in the index function, the first argument is treated as the element to be searched and the second argument is the index from where the searching begins. 

list_name.index(element , start)

Output :

3

Code #6: The end index passed as argument is not included 

The third argument which is the end, itself is not included in the range from start to end, i.e the searching takes place from start to end-1 index. 

Output:

Traceback (most recent call last):
  File "/home/3cbe5b7d0595ab3f8564f16af7a15172.py", line 9, in <module>
    print(list1.index(9 , 1 , 4))
ValueError: 9 is not in list

Output:

4

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