What is the average and worst-case complexity of insertion and indexing in a Python dictionary?

In Python, a dictionary is implemented based on a hash table. The average time complexity of insert and index operations (search by key) is O(1), meaning constant time. In the worst case, when there are many collisions, the complexity can degrade to O(n), where n is the number of elements in the dictionary. However, thanks to good hashing and dynamic resizing of the table, the worst case is very rare.