Python list | index() - GeeksforGeeks

index() is an inbuilt function in Python, which searches for given element from 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 :

# 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')) 

Output :

3
0

Code #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 )) 

Output :

7
4
3

Code #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'))) 

Output :

3
4

Code #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)) 

Output :

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

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