Why is a list access O(1) in Python?

Question

I understand that a list is different from an array. But still, O(1)? That would mean accessing an element in a list would be as fast as accessing an element in a dict, which we

Answer 1

Get item is getting an item in a specific index, while lookup means searching if some element exists in the list. To do so, unless the list is sorted, you will need to iterate all elements, and have O(n) Get Item operations, which leads to O(n) lookup.

A dictionary is maintaining a smart data structure (hash table) under the hood, so you will not need to query O(n) times to find if the element exists, but a constant number of times (average case), leading to O(1) lookup.