IndexError: list index out of range

What causes this error

You accessed a list, tuple, or string at an index that does not exist. The index is either too large (beyond the last element) or too negative. Empty sequences will raise this for any index.

How to fix it

Check the sequence length with len() before accessing by index. Use negative indexing carefully (list[-1] for the last item). Handle empty sequences explicitly. Use try-except IndexError if the length is uncertain.

lst = [1, 2, 3]; lst[5]  # IndexError: list index out of range