Python list | index()

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 :

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# 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'))

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Output :

3
0

 
Code #2 :

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# 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 ))

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Output :

7
4
3

 

Code #3 :

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# 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')))

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Output :

3
4

 
Code #4 : ValueError

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# Python3 program for demonstration  
# of index() method error
   
   
list1 = [1, 2, 3, 4, 1, 1, 1, 4, 5]
  
# Return ValueError
print(list1.index(10))

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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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