Python List index()

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

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')   # 2
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