Python List index() method

Python List index() method

The list.index () method in Python returns the position at the first occurrence of the specified value.

Syntax

list.index(x[, start[, end]])

Parameter

element – This parameter represents the element whose lowest index will be returned.

start (Optional) – It signifies the position from where the search begins.

end (Optional) – This parameter signifies the position from where the search ends.

Return

This function returns a zero-based index in the list of the first item whose value is equal to x or raises a ValueError if there is no such item.

Example 1

# Python program for demonstration
# of list.index() method 
num_list = [11, 12, 13, 14, 11, 11, 11, 14, 15] 
# printing the index of '4' in num_list 
print("The index of value 14:",num_list.index(14)) 
month_list = ['January', 'Febuary', 'March', 'April', 'May','June']  
# printing the index of 'March' in list2  
print("The index value of string value March: ",month_list.index('March')) 

Output

The index of value 14: 3
The index value of string value March:  2 

Example 2

# Python program for demonstration
# of list.index() method 
num_list = [11, 12, 13, 14, 11, 11, 11, 14, 15] 
# printing the index of '4' in num_list  
print("The index of value 14:",num_list.index(14)) 
month_list = ['January', 'Febuary', 'March', 'April', 'May','June'] 
# printing the index of 'July' in list2, will raise a ValueError as there is no such item.
print("The index value of string value July: ",month_list.index('July')) 

Output

The index of value 14: 3
 Traceback (most recent call last):
   File "main.py", line 12, in <module>
     print("The index value of string value July: ",month_list.index('July')) 
 ValueError: 'July' is not in list