{"id":128893,"date":"2022-10-14T17:51:24","date_gmt":"2022-10-14T17:51:24","guid":{"rendered":"https:\/\/blog.finxter.com\/?p=789184"},"modified":"2022-10-14T17:51:24","modified_gmt":"2022-10-14T17:51:24","slug":"can-a-python-dictionary-have-a-list-as-a-value","status":"publish","type":"post","link":"https:\/\/sickgaming.net\/blog\/2022\/10\/14\/can-a-python-dictionary-have-a-list-as-a-value\/","title":{"rendered":"Can a Python Dictionary Have a List as a Value?"},"content":{"rendered":"\n
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5\/5 – (1 vote) <\/div>\n<\/div>\n

Question<\/h2>\n

\"\ud83d\udcac\" Question<\/strong>: Can you use lists as values<\/em> of a dictionary in Python?<\/p>\n

This short article will answer your question. So, let’s get started right away with the answer:<\/p>\n

Answer<\/h2>\n

You can use Python lists<\/a> as dictionary values. In fact, you can use arbitrary Python objects as dictionary<\/a> values and all hashable<\/a> objects as dictionary keys. You can define a list [1, 2]<\/code> as a dict value either with dict[key] = [1, 2]<\/code> or with d = {key: [1, 2]}<\/code>.<\/p>\n

Here’s a concrete example showing how to create a dictionary friends<\/code> where each dictionary value is in fact a list of friends:<\/p>\n

friends = {'Alice': ['Bob', 'Carl'], 'Bob': ['Alice'], 'Carl': []} print('Alice friends: ', friends['Alice'])\n# Alice friends: ['Bob', 'Carl'] print('Bob friends: ', friends['Bob'])\n# Bob friends: ['Alice'] print('Carl friends: ', friends['Carl'])\n# Carl friends: []<\/pre>\n
Note that you can also assign lists as values of specific keys by using the dictionary assignment<\/a> operation like so:<\/p>\n
friends = dict()\nfriends['Alice'] = ['Bob', 'Carl']\nfriends['Bob'] = ['Alice']\nfriends['Carl'] = [] print('Alice friends: ', friends['Alice'])\n# Alice friends: ['Bob', 'Carl'] print('Bob friends: ', friends['Bob'])\n# Bob friends: ['Alice'] print('Carl friends: ', friends['Carl'])\n# Carl friends: []\n<\/pre>\n
Can I Use Lists as Dict Keys?<\/h2>\n
You cannot use lists as dictionary keys because lists are mutable<\/a> and therefore not hashable<\/a>. As dictionaries are built on hash tables, all keys must be hashable or Python raises an error message<\/a>.<\/p>\n
Here’s an example:<\/p>\n
d = dict()\nmy_list = [1, 2, 3]\nd[my_list] = 'abc'\n<\/pre>\n
This leads to the following error message:<\/p>\n
Traceback (most recent call last): File \"C:\\Users\\xcent\\Desktop\\code.py\", line 3, in <module> d[my_list] = 'abc'\nTypeError: unhashable type: 'list'<\/pre>\n
To fix this, convert the list to a Python tuple<\/a> and use the Python tuple as a dictionary key. Python tuples are immutable and hashable and, therefore, can be used as set elements or dictionary keys.<\/p>\n
Here’s the same example after converting the list to a tuple<\/a>—it works! \"\ud83c\udf89\"<\/p>\n
d = dict()\nmy_list = [1, 2, 3]\nmy_tuple = tuple(my_list)\nd[my_tuple] = 'abc'\n<\/pre>\n
Before you go, maybe you want to join our free email academy<\/a> of ambitious learners like you? The goal is to become 1% better every single day (as a coder). We also have cheat sheets! \"\ud83d\udc47\" <\/p>\n","protected":false},"excerpt":{"rendered":"
5\/5 – (1 vote) Question Question: Can you use lists as values of a dictionary in Python? This short article will answer your question. So, let’s get started right away with the answer: Answer You can use Python lists as dictionary values. In fact, you can use arbitrary Python objects as dictionary values and all […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[857],"tags":[73,468,528],"class_list":["post-128893","post","type-post","status-publish","format-standard","hentry","category-python-tut","tag-programming","tag-python","tag-tutorial"],"_links":{"self":[{"href":"https:\/\/sickgaming.net\/blog\/wp-json\/wp\/v2\/posts\/128893","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sickgaming.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/sickgaming.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/sickgaming.net\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/sickgaming.net\/blog\/wp-json\/wp\/v2\/comments?post=128893"}],"version-history":[{"count":0,"href":"https:\/\/sickgaming.net\/blog\/wp-json\/wp\/v2\/posts\/128893\/revisions"}],"wp:attachment":[{"href":"https:\/\/sickgaming.net\/blog\/wp-json\/wp\/v2\/media?parent=128893"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/sickgaming.net\/blog\/wp-json\/wp\/v2\/categories?post=128893"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/sickgaming.net\/blog\/wp-json\/wp\/v2\/tags?post=128893"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}