How is the time complexity of searching for an element by key in a dictionary data store evaluated?

In Python, a dictionary is implemented based on a hash table, so searching for an element by key is on average performed in O(1) — constant time. This is achieved through computing the hash function of the key and quick access to the corresponding cell.

However, in the worst case, for example, with a large number of collisions, the time complexity can degrade to O(n), where n is the number of elements in the dictionary. In practice, such cases are rare due to good implementation of hash functions and dynamic resizing of the dictionary.