How to Fix IndexError: List Index Out of Range in Python

A Python list index out of range error stopped a client’s nightly sales report last month. The list had three prices; the loop asked for a fourth.

Wrapping the loop in try hides the crash, but the total is still wrong, so I fix the index instead.

Quick answer: a list with n items only has indexes 0 to n - 1 (or -n to -1). Loop over the items directly, and check 0 <= i < len(items) before reading an index you didn’t create:

for price in prices:          # no index, no IndexError
    total += price

value = items[i] if 0 <= i < len(items) else None

In this tutorial, I’ll fix the Python list index out of range error for each cause I keep running into on real projects. Outputs come from Python 3.12.5.

What does IndexError: list index out of range mean?

Python raises it when items[i] points past either end of the list. Here’s a three-customer queue:

queue = ["Emily", "James", "Olivia"]   # three customers -> indexes 0, 1, 2

print(len(queue), queue[0], queue[2], queue[-1])
print(queue[1:10])                      # a slice never raises
print(queue[3])                         # one past the end

Output:

3 Emily Olivia Olivia
['James', 'Olivia']
Traceback (most recent call last):
  File "C:\pyguides\queue_index.py", line 5, in <module>
    print(queue[3])                         # one past the end
          ~~~~~^^^
IndexError: list index out of range

The line above the error shows the failing lookup. It’s a runtime error, like the others in my overview of the types of errors in Python.

Fix the off-by-one error in a for loop

Most IndexErrors I debug come from loops that count from 1, the way you’d count on paper:

prices = [19.99, 5.49, 12.00]
total = 0
for i in range(1, len(prices) + 1):    # counting items from 1
    total += prices[i]
    print(f"item {i}: ${prices[i]:.2f}")
print(f"Total: ${total:.2f}")

Output:

item 1: $5.49
item 2: $12.00
Traceback (most recent call last):
  File "C:\pyguides\prices_loop_bug.py", line 4, in <module>
    total += prices[i]
             ~~~~~~^^^
IndexError: list index out of range

It skipped $19.99 at index 0, printed two items, then crashed at index 3. A while i <= len(prices) loop fails the same way. Let enumerate() do the numbering instead:

prices = [19.99, 5.49, 12.00]
total = 0
for n, price in enumerate(prices, start=1):   # numbers from 1, no indexing
    total += price
    print(f"item {n}: ${price:.2f}")
print(f"Total: ${total:.2f}")

Output:

item 1: $19.99
item 2: $5.49
item 3: $12.00
Total: $37.48

start=1 only changes the label, never the lookup. More patterns are in my guides to enumerate() in Python and getting the index in a for loop.

Check for an empty list before reading the first item

A filter that matches nothing returns [], and [][0] fails even though index 0 looks safe. Here no order comes from New York:

orders = [{"customer": "Emily", "state": "TX"}, {"customer": "James", "state": "CA"}]
ny = [o for o in orders if o["state"] == "NY"]
print("NY orders:", len(ny))

first = ny[0] if ny else None            # guard the empty case
print("first NY order:", first)
print("latest:", orders[-1]["customer"] if orders else None)

Output:

NY orders: 0
first NY order: None
latest: James

An empty list is falsy, so ny[0] if ny else None covers it, and the same guard protects items[-1]. Other checks are in how to check if a list is empty in Python.

Why does deleting items in a loop cause IndexError?

range(len(amounts)) is fixed when the loop starts. Each del shrinks the list, so the last indexes no longer exist:

amounts = [120.50, 0.00, 42.10, 0.00]
try:
    for i in range(len(amounts)):
        if amounts[i] == 0:
            del amounts[i]            # the list shrinks, range() doesn't
except IndexError as err:
    print("del in a loop ->", err, "| left:", amounts)

amounts = [120.50, 0.00, 42.10, 0.00]
amounts = [a for a in amounts if a != 0]
print("comprehension ->", amounts)

Output:

del in a loop -> list index out of range | left: [120.5, 42.1]
comprehension -> [120.5, 42.1]

Build a new list instead. A list comprehension is the shortest way, and it never touches a stale index.

Guard list indexes from split() and user input

When the index comes from outside your code, like a CSV line or user input, check the length first:

rows = [
    "2026-03-02,Emily,120.50",
    "2026-03-03,James",           # amount missing
    "2026-03-04,Olivia,42.10",
]
for line in rows:
    parts = line.split(",")
    if len(parts) < 3:
        print(f"skipped {line!r}: expected 3 fields, got {len(parts)}")
        continue
    date, name, amount = parts
    print(f"{date} {name:<7} ${float(amount):.2f}")

Output:

2026-03-02 Emily   $120.50
skipped '2026-03-03,James': expected 3 fields, got 2
2026-03-04 Olivia  $42.10

For a single index you got from input, check 0 <= i < len(items) first. For arrays, see checking if an array index exists in Python.

Common errors and how to fix them

Message	Usual cause	Fix
list index out of range	Index >= len(), or an empty list	Loop over items, guard with if items
list assignment index out of range	Assigning past the end	Use append() instead
string index out of range	Same bug on a string	String IndexError fix
tuple index out of range	Unpacking or format() args	Tuple IndexError fix
KeyError	Missing dictionary key, not an index	Dictionary KeyError fix

Keep going with these list guides:

• Get the index of an element in a Python list
• Find the size of a Python list
• Slice lists in Python
• The Python list pop() method

Frequently asked questions