How to Fix: IndexError: list index out of range in Python

If you’re working with Python lists, you will likely encounter the “IndexError: list index out of range” error. It’s practically a rite of passage. This IndexError occurs when your code tries to access a list at an index that doesn’t exist. But the good news is, it’s very simple to understand and fix.

What Does IndexError: list index out of range Mean?

In plain English, this error means:

“You are trying to access an item in a list using an index (position) that does not exist.” An IndexError: list index out of range typically happens when you forget that Python lists start at index 0.

Remember that Python lists are 0-indexed. This means the first item is at index 0, the second is at index 1, and so on.

Let’s look at this list:

my_list = ["apple", "banana", "cherry"]

• my_list[0] is “apple”
• my_list[1] is “banana”
• my_list[2] is “cherry”

The length of the list is 3, but the last valid index is 2. Trying to access an index beyond this will result in an IndexError: list index out of range.

If you try to access my_list[3], Python will raise an IndexError because there is no item at index 3.

3 Common Causes and Their Fixes

Let’s diagnose the most common reasons you’ll see this error and how to fix them.

Cause 1: The “Off-by-One” Error in a for loop

This is the most common cause. You are looping using a range that is one-too-many, leading to an IndexError: list index out of range.

Problem Code:

my_list = ["apple", "banana", "cherry"]
list_length = len(my_list)  # This is 3

# This loops with i as 0, 1, 2, AND 3
for i in range(list_length + 1):
  print(my_list[i])  # This will FAIL when i becomes 3

The Fix: Never use range(len(my_list) + 1). The range(len(my_list)) function already gives you the correct indices: 0, 1, 2.

Correct Code (Option 1 – Using range):

my_list = ["apple", "banana", "cherry"]
list_length = len(my_list)  # This is 3

# range(3) gives 0, 1, 2. This is correct!
for i in range(list_length):
  print(my_list[i])

Correct Code (Option 2 – The “Pythonic” Way): A much cleaner way to loop is to iterate over the items directly, without worrying about indices at all.

my_list = ["apple", "banana", "cherry"]

for item in my_list:
  print(item)

Cause 2: Accessing an Item in an Empty List

If you try to access any index on a list that is empty, it will fail and result in an IndexError: list index out of range.

Problem Code:

user_cart = []  # The list is empty

# You try to get the "first item"
print(user_cart[0])

The Fix: Always check if a list is not empty before you try to access an item from it. An empty list evaluates to False in an if statement.

Correct Code:

user_cart = []

if user_cart:  # This is the same as "if len(user_cart) > 0"
  print(f"Your first item is: {user_cart[0]}")
else:
  print("Your cart is empty.")

Cause 3: Using the Wrong Length (e.g., len vs. len - 1)

This often happens when you’re trying to get the last item in a list, causing an IndexError: list index out of range if done incorrectly.

Problem Code:

my_list = ["apple", "banana", "cherry"]
list_length = len(my_list)  # list_length is 3

# You try to get the item at index 3
last_item = my_list[list_length]  # This fails

The Fix: The last item is always at index len(my_list) - 1. However, Python gives you a much better way: negative indexing.

my_list[-1] always refers to the last item, my_list[-2] to the second-to-last, and so on.

Correct Code:

my_list = ["apple", "banana", "cherry"]

# Get the last item
last_item = my_list[-1]

print(last_item)  # Output: cherry

This is safer and more readable.