Python Language Dictionary

Internal

• Python Language

Overview

A dictionary is a mutable collection of key-value pairs. The pairs can be accessed and modified. Each key is unique within the key set, and can be an instance of any immutable type: boolean, integer, float, tuple, string, etc. In other programming languages, the same data structure is referred to as "associative array" or "hash tables" or "hash maps".

Key Discussion

The keys 1 and True are equivalent. Why?

Create a Dictionary

A new dictionary instance is declared using the {...} syntax. The dictionary can be empty

d = {}

or it can be populated with values:

d = {'a': 'b', 1: 2, True: "this is true"}

It is good form to insert a space after :.

Access a Dictionary

Access Individual Elements

[], get()

An attempt to access an inexistent key ends up in a KeyError exception being thrown.

Test the existence of a key.

Access:

d["key"]

Modify a Dictionary

Modify Individual Elements

Add, modify, delete.