Python List index()

The index() method returns the index of the specified element in the list.

Example

animals = ['cat', 'dog', 'rabbit', 'horse']

# get the index of 'dog' index = animals.index('dog')
print(index) # Output: 1

Syntax of List index()

The syntax of the list index() method is:

list.index(element, start, end)

list index() parameters

The list index() method can take a maximum of three arguments:

  • element - the element to be searched
  • start (optional) - start searching from this index
  • end (optional) - search the element up to this index

Return Value from List index()

  • The index() method returns the index of the given element in the list.
  • If the element is not found, a ValueError exception is raised.

Note: The index() method only returns the first occurrence of the matching element.


Example 1: Find the index of the element

# vowels list
vowels = ['a', 'e', 'i', 'o', 'i', 'u']

# index of 'e' in vowels
index = vowels.index('e')
print('The index of e:', index) # element 'i' is searched # index of the first 'i' is returned
index = vowels.index('i')
print('The index of i:', index)

Output

The index of e: 1
The index of i: 2

Example 2: Index of the Element not Present in the List

# vowels list
vowels = ['a', 'e', 'i', 'o', 'u']

# index of 'p' is vowels
index = vowels.index('p')
print('The index of p:', index)

Output

ValueError: 'p' is not in list

Example 3: Working of index() With Start and End Parameters

# alphabets list
alphabets = ['a', 'e', 'i', 'o', 'g', 'l', 'i', 'u']

# index of 'i' in alphabets
index = alphabets.index('e') # 1
print('The index of e:', index) # 'i' after the 4th index is searched
index = alphabets.index('i', 4) # 6
print('The index of i:', index) # 'i' between 3rd and 5th index is searched
index = alphabets.index('i', 3, 5) # Error!
print('The index of i:', index)

Output

The index of e: 1
The index of i: 6
Traceback (most recent call last):
  File "*lt;string>", line 13, in 
ValueError: 'i' is not in list

Also Read: Python Program to Access Index of a List Using for Loop

Challenge

Write a function to find the index of a given element in a list.

  • For example, with inputs [1, 2, 3, 4, 5] and 3, the output should be 2.
Did you find this article helpful?