Python High Performance - Second Edition

Dictionaries

Dictionaries are extremely versatile and extensively used in the Python language. Dictionaries are implemented as hash maps and are very good at element insertion, deletion, and access; all these operations have an average O(1) time complexity. 

In Python versions up to 3.5, dictionaries are unordered collections. Since Python 3.6, dictionaries are capable of maintaining their elements by order of insertion.

A hash map is a data structure that associates a set of key-value pairs. The principle behind hash maps is to assign a specific index to each key so that its associated value can be stored in an array. The index can be obtained through the use of a hash function; Python implements hash functions for several data types. As ...