{"id":85,"date":"2020-10-03T01:20:06","date_gmt":"2020-10-03T01:20:06","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=85"},"modified":"2025-03-27T03:01:37","modified_gmt":"2025-03-27T03:01:37","slug":"python-dictionary","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/python-basics\/python-dictionary\/","title":{"rendered":"Python Dictionary"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn about Python dictionary type that allows you to create a collection of key-value pairs.<\/p>\n\n\n\n

Introduction to the Python Dictionary type #<\/a><\/h2>\n\n\n\n

A Python dictionary is a collection of key-value pairs where each key is associated with a value. <\/p>\n\n\n\n

A value in the key-value pair can be a number<\/a>, a string<\/a>, a list<\/a>, a tuple<\/a>, or even another dictionary. In fact, you can use a value of any valid type in Python as the value in the key-value pair.<\/p>\n\n\n\n

A key in the key-value pair must be immutable. In other words, the key cannot be changed, for example, a number, a string, a tuple, etc.<\/p>\n\n\n\n

Python uses curly braces {}<\/code> to define a dictionary. Inside the curly braces, you can place zero, one, or many key-value pairs.<\/p>\n\n\n\n

The following example defines an empty dictionary:<\/p>\n\n\n

empty_dict = {}<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
To find the type of a dictionary, you use the type()<\/code> function as follows:<\/p>\n\n\n
empty_dict = {}\n\nprint(type(empty_dict))<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
<class<\/span> 'dict<\/span>'><\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The following example defines a dictionary with some key-value pairs:<\/p>\n\n\n
person = {\n    'first_name'<\/span>: 'John'<\/span>,\n    'last_name'<\/span>: 'Doe'<\/span>,\n    'age'<\/span>: 25<\/span>,\n    'favorite_colors'<\/span>: ['blue'<\/span>, 'green'<\/span>],\n    'active'<\/span>: True<\/span>\n}<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The person<\/code> dictionary has five key-value pairs that represent the first name, last name, age, favorite colors, and active status.<\/p>\n\n\n\n
Accessing values in a Dictionary #<\/a><\/h2>\n\n\n\n
To access a value by key from a dictionary, you can use the square bracket notation or the get()<\/code> method. <\/p>\n\n\n\n
1) Using square bracket notation #<\/a><\/h3>\n\n\n\n
To access a value associated with a key, you place the key inside square brackets:<\/p>\n\n\n
dict[key]<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The following shows how to get the values associated with the key first_name<\/code> and last_name<\/code> in the person<\/code> dictionary:<\/p>\n\n\n
person = {\n    'first_name'<\/span>: 'John'<\/span>,\n    'last_name'<\/span>: 'Doe'<\/span>,\n    'age'<\/span>: 25<\/span>,\n    'favorite_colors'<\/span>: ['blue'<\/span>, 'green'<\/span>],\n    'active'<\/span>: True<\/span>\n}\nprint(person['first_name'<\/span>])\nprint(person['last_name'<\/span>])<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
John\nDoe<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
2) Using the get() method #<\/a><\/h3>\n\n\n\n
If you attempt to access a key that doesn’t exist, you’ll get an error. For example:<\/p>\n\n\n
person = {\n    'first_name'<\/span>: 'John'<\/span>,\n    'last_name'<\/span>: 'Doe'<\/span>,\n    'age'<\/span>: 25<\/span>,\n    'favorite_colors'<\/span>: ['blue'<\/span>, 'green'<\/span>],\n    'active'<\/span>: True<\/span>\n}\n\nssn = person['ssn'<\/span>]<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Error:<\/p>\n\n\n
Traceback (most recent call last):\n  File \"dictionary.py\"<\/span>, line 15<\/span>, in<\/span> <module>\n    ssn = person['ssn'<\/span>]\nKeyError: 'ssn'<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
To avoid this error, you can use the get()<\/code> method of the dictionary:<\/p>\n\n\n
person = {\n    'first_name'<\/span>: 'John'<\/span>,\n    'last_name'<\/span>: 'Doe'<\/span>,\n    'age'<\/span>: 25<\/span>,\n    'favorite_colors'<\/span>: ['blue'<\/span>, 'green'<\/span>],\n    'active'<\/span>: True<\/span>\n}\n\nssn = person.get('ssn'<\/span>)\nprint(ssn)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
None<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
If the key doesn’t exist, the get()<\/code> method returns None<\/code> instead of throwing a KeyError<\/code>. Note that None<\/code> means no value exists.<\/p>\n\n\n\n
The get()<\/code> method also returns a default value when the key doesn’t exist by passing the default value to its second argument.<\/p>\n\n\n\n
The following example returns the '000-00-0000'<\/code> string if the ssn<\/code> key doesn’t exist in the person<\/code> dictionary:<\/p>\n\n\n
person = {\n    'first_name'<\/span>: 'John'<\/span>,\n    'last_name'<\/span>: 'Doe'<\/span>,\n    'age'<\/span>: 25<\/span>,\n    'favorite_colors'<\/span>: ['blue'<\/span>, 'green'<\/span>],\n    'active'<\/span>: True<\/span>\n}\n\nssn = person.get('ssn'<\/span>, '000-00-0000'<\/span>)\nprint(ssn)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
000<\/span>-00<\/span>-0000<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Adding new key-value pairs #<\/a><\/h2>\n\n\n\n
Since a dictionary has a dynamic structure, you can add new key-value pairs to it at any time.<\/p>\n\n\n\n
To add a new key-value pair to a dictionary, you specify the name of the dictionary followed by the new key in square brackets along with the new value. <\/p>\n\n\n\n
The following example adds a new key-value pair to the person<\/code> dictionary:<\/p>\n\n\n
person['gender'<\/span>] = 'Famale'<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Modifying values in a key-value pair #<\/a><\/h2>\n\n\n\n
To modify a value associated with a key, you specify the dictionary name with the key in square brackets and the new value associated with the key:<\/p>\n\n\n
dict[key] = new_value<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The following example modifies the value associated with the age<\/code> of the person<\/code> dictionary:<\/p>\n\n\n
person = {\n    'first_name'<\/span>: 'John'<\/span>,\n    'last_name'<\/span>: 'Doe'<\/span>,\n    'age'<\/span>: 25<\/span>,\n    'favorite_colors'<\/span>: ['blue'<\/span>, 'green'<\/span>],\n    'active'<\/span>: True<\/span>\n}\n\nperson['age'<\/span>] = 26<\/span>\n\nprint(person)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
{'first_name'<\/span>: 'John'<\/span>, 'last_name'<\/span>: 'Doe'<\/span>, 'age'<\/span>: 26<\/span>, 'favorite_colors'<\/span>: ['blue'<\/span>, 'green'<\/span>], 'active'<\/span>: True<\/span>}<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Removing key-value pairs #<\/a><\/h2>\n\n\n\n
To remove a key-value pair by a key, you use the del<\/code> statement:<\/p>\n\n\n
del<\/span> dict[key]<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
In this syntax, you specify the dictionary name and the key that you want to remove. <\/p>\n\n\n\n
The following example removes the key 'active'<\/code> from the person<\/code> dictionary:<\/p>\n\n\n
person = {\n    'first_name'<\/span>: 'John'<\/span>,\n    'last_name'<\/span>: 'Doe'<\/span>,\n    'age'<\/span>: 25<\/span>,\n    'favorite_colors'<\/span>: ['blue'<\/span>, 'green'<\/span>],\n    'active'<\/span>: True<\/span>\n}\n\ndel<\/span> person['active'<\/span>]\nprint(person)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
{'first_name'<\/span>: 'John'<\/span>, 'last_name'<\/span>: 'Doe'<\/span>, 'age'<\/span>: 25<\/span>, 'favorite_colors'<\/span>: ['blue'<\/span>, 'green'<\/span>]}<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Looping through a dictionary #<\/a><\/h2>\n\n\n\n
To examine a dictionary, you can use a for<\/code> loop to iterate over its key-value pairs, or keys, or values.<\/p>\n\n\n\n
Note that since Python 3.7,  when you loop through a dictionary, you’ll get the key-value pairs in the same order that you insert them.<\/p>\n\n\n\n
Looping all key-value pairs in a dictionary #<\/a><\/h3>\n\n\n\n
Python dictionary provides a method called items()<\/code> that returns an object which contains a list of key-value pairs as tuples in a list.<\/p>\n\n\n\n
For example:<\/p>\n\n\n
person = {\n    'first_name'<\/span>: 'John'<\/span>,\n    'last_name'<\/span>: 'Doe'<\/span>,\n    'age'<\/span>: 25<\/span>,\n    'favorite_colors'<\/span>: ['blue'<\/span>, 'green'<\/span>],\n    'active'<\/span>: True<\/span>\n}\n\nprint(person.items())<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
dict_items([('first_name'<\/span>, 'John'<\/span>), ('last_name'<\/span>, 'Doe'<\/span>), ('age'<\/span>, 25<\/span>), ('favorite_colors'<\/span>, ['blue'<\/span>, 'green'<\/span>]), ('active'<\/span>, True<\/span>)])<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
person = {\n    'first_name'<\/span>: 'John'<\/span>,\n    'last_name'<\/span>: 'Doe'<\/span>,\n    'age'<\/span>: 25<\/span>,\n    'favorite_colors'<\/span>: ['blue'<\/span>, 'green'<\/span>],\n    'active'<\/span>: True<\/span>\n}\n\nfor<\/span> key, value in<\/span> person.items():\n    print(f\"{key}<\/span>: {value}<\/span>\"<\/span>)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
first_name: John\nlast_name: Doe\nage: 25<\/span>\nfavorite_colors: ['blue'<\/span>, 'green'<\/span>]\nactive: True<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Note that you can use any variable name in the for<\/code> loop. They don’t have to be the key<\/code> and value<\/code>.<\/p>\n\n\n\n
Looping through all the keys in a dictionary #<\/a><\/h3>\n\n\n\n
Sometimes, you just want to loop through all keys in a dictionary. In this case, you can use a for<\/code> loop with the keys()<\/code> method.<\/p>\n\n\n\n
The keys()<\/code> method returns an object that contains a list of keys in the dictionary.<\/p>\n\n\n\n
For example:<\/p>\n\n\n
person = {\n    'first_name'<\/span>: 'John'<\/span>,\n    'last_name'<\/span>: 'Doe'<\/span>,\n    'age'<\/span>: 25<\/span>,\n    'favorite_colors'<\/span>: ['blue'<\/span>, 'green'<\/span>],\n    'active'<\/span>: True<\/span>\n}\n\nfor<\/span> key in<\/span> person.keys():\n    print(key)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
first_name\nlast_name\nage\nfavorite_colors\nactive<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
In fact, looping through all keys is the default behavior when looping through a dictionary. Therefore, you don’t need to use the keys()<\/code> method. <\/p>\n\n\n\n
The following code returns the same output as the one in the above example:<\/p>\n\n\n
person = {\n    'first_name'<\/span>: 'John'<\/span>,\n    'last_name'<\/span>: 'Doe'<\/span>,\n    'age'<\/span>: 25<\/span>,\n    'favorite_colors'<\/span>: ['blue'<\/span>, 'green'<\/span>],\n    'active'<\/span>: True<\/span>\n}\n\nfor<\/span> key in<\/span> person:\n    print(key)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Looping through all the values in a dictionary #<\/a><\/h3>\n\n\n\n
The values()<\/code> method returns a list of values without any keys. <\/p>\n\n\n\n
To loop through all the values in a dictionary, you use a for loop with the values()<\/code> method:<\/p>\n\n\n
person = {\n    'first_name'<\/span>: 'John'<\/span>,\n    'last_name'<\/span>: 'Doe'<\/span>,\n    'age'<\/span>: 25<\/span>,\n    'favorite_colors'<\/span>: ['blue'<\/span>, 'green'<\/span>],\n    'active'<\/span>: True<\/span>\n}\n\nfor<\/span> value in<\/span> person.values():\n    print(value)\n<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
John\nDoe\n25<\/span>\n['blue'<\/span>, 'green'<\/span>]\nTrue<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Summary #<\/a><\/h2>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
To iterate over all key-value pairs in a dictionary, you use a for<\/code> loop with two variable key<\/code> and value<\/code> to unpack each tuple<\/a> of the list:<\/p>\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Typically, you define an empty dictionary before a loop, either for loop <\/a>or while loop<\/a>. And inside the loop, you add key-value pairs to the dictionary.<\/p>\n\n\n\n