Python Language Dictionary: Difference between revisions

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=Create a Dictionary=
=Create a Dictionary=


A new dictionary instance is declared using the <code>{</code><code>}</code> syntax. The dictionary can be empty
A new dictionary instance is declared using the <code>{...}</code> syntax. The dictionary can be empty
<syntaxhighlight lang='python'>
<syntaxhighlight lang='python'>
d = {}
d = {}

Revision as of 19:56, 16 February 2022

Internal

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".

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"]

Get All Keys

Get All Values

Modify a Dictionary

Modify Individual Elements

Add, modify, delete.

Combine Dictionaries