Python Language Dictionary: Difference between revisions
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=Overview= | =Overview= | ||
A dictionary is a mutable collection of key-value pairs. The pairs can be [[#Access_a_Dictionary|accessed]] and [[#Modify_a_Dictionary|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 "[[Bash_Arrays#Associative_Arrays|associative array]]" or "[[Hash_Table#Overview|hash tables]]" or "hash maps". | A dictionary is a mutable collection of key-value pairs. The pairs can be [[#Access_a_Dictionary|accessed]] and [[#Modify_a_Dictionary|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 "[[Bash_Arrays#Associative_Arrays|associative array]]" or "[[Hash_Table#Overview|hash tables]]" or "hash maps". | ||
=Key Discussion= | |||
=Create a Dictionary= | =Create a Dictionary= |
Revision as of 19:57, 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".
Key Discussion
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.