How to Check if an Index Exists in Python Lists

When working with lists in Python, sometimes we need to check if a particular index exists. This is important because if we try to access an index that is out of range, we will get an error. Let's look at some simple ways to check if an index exists in a Python list.

The easiest methods to check if given index exists in list are using try and except or comparing index to length of the list using len() method.

Using len() method

To check if an index exists, we can compare it with the length of list. If the index is less than the length, it exists.

a = [10, 20, 30, 40]
index = 3
# Using len() to check index
if index < len(a):
    print(a[index])
else:
    print("Index does not exist!")

Using try and except

The easiest way to check if an index exists is by using a try and except block. This method will try to access the index, and if it doesn’t exist, Python will handle the error without crashing the program.

a = [10, 20, 30, 40]
try:
    print(a[5])
except IndexError:
    print("Index does not exist!")

Index does not exist!

Using in Operator

Another simple method is to check if the index is within the valid range of the list by using the in operator. This checks if the index is within the range of 0 to len(lst) - 1.

lst = [10, 20, 30, 40]
index = 2
if index in range(len(lst)):
    print(lst[index])
else:
    print("Index does not exist!")

30