Python: A Primer on Dictionaries

Python dictionaries are indexed by keys. Strings and numbers can always be keys. Tuples can be too if they contain strings, numbers, or tuples. Dictionaries consist of key and value pairs.

An empty pair of braces creates an empty dictionary

empty_dictionary = {}

You can list a dictionary’s keys

my_dictionary = {'User 1': 'AwesomePassword', 'User 2': 'AnotherPassword'}
​
list(my_dictionary)

Sort it

my_dictionary = {'User 1': 'AwesomePassword', 'User 2': 'AnotherPassword'}
​
sorted(my_dictionary)

Delete an item

my_dictionary = {'User 1': 'AwesomePassword', 'User 2': 'AnotherPassword'}
​
del my_dictionary['User 1']

Search a list

my_dictionary = {'User 1': 'AwesomePassword', 'User 2': 'AnotherPassword'}
​
included = 'User 1' in my_dictionary
​
not_included = 'User 3894' not in my_dictionary

You can also create a dictionary with a comprehension

import string
​
alphabet_dictionary = {k: v for k, v in enumerate(string.ascii_lowercase)}

You can loop

import string
​
alphabet_dictionary = {k: v for k, v in enumerate(string.ascii_lowercase)}
​
for key, val in alphabet_dictionary.items():
    print(key, val)

Loop in reverse

import string
​
alphabet_dictionary = {k: v for k, v in enumerate(string.ascii_lowercase)}
​
for key, val in reversed(alphabet_dictionary.items()):
    print(key, val)

Loop in sorted order

import string
​
alphabet_dictionary = {k: v for k, v in enumerate(string.ascii_lowercase)}
​
for key, val in sorted(alphabet_dictionary.items()):
    print(key, val)