{"id":64,"date":"2024-01-25T09:26:48","date_gmt":"2024-01-25T09:26:48","guid":{"rendered":"https:\/\/learnpython.elegantwallp.com\/?p=64"},"modified":"2024-01-25T09:26:51","modified_gmt":"2024-01-25T09:26:51","slug":"python-list","status":"publish","type":"post","link":"https:\/\/learnpython.elegantwallp.com\/2024\/01\/25\/python-list\/","title":{"rendered":"Python List"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you\u2019ll learn about Python List type and how to manipulate list elements effectively.<\/p>\n\n\n\n

What is a List<\/h2>\n\n\n\n

A list is an ordered collection of items.<\/p>\n\n\n\n

Python uses the square brackets ([]<\/code>) to indicate a list. The following shows an empty list:<\/p>\n\n\n\n

empty_list = []<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Typically, a list contains one or more items. To separate two items, you use a comma (,). For example:<\/p>\n\n\n\n
todo_list = ['Learn Python List','How to manage List elements']<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n\n\n
Since a list often contains many items, it\u2019s a good practice to name it using plural nouns e.g., numbers<\/code>, colors<\/code>, and shopping_carts<\/code>.<\/p>\n\n\n\n
The following example defines a list of six\u00a0numbers:<\/p>\n\n\n\n
numbers = [1, 3, 2, 7, 9, 4]<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
If you print out the list, you\u2019ll see its representation including the square brackets. For example:<\/p>\n\n\n\n
print(numbers)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
[1, 3, 2, 7, 9, 4]<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n\n\n
The following shows how to define a list of\u00a0strings:<\/p>\n\n\n\n
colors = ['red', 'green', 'blue'] print(colors)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
['red', 'green', 'blue']<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n\n\n
A list can contain other lists. The following example defines a list of lists:<\/p>\n\n\n\n
coordinates = [[0, 0], [100, 100], [200, 200]] print(coordinates)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n\n\n
[[0, 0], [100, 100], [200, 200]]<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Accessing elements in a list<\/h2>\n\n\n\n
Since a list is an ordered collection, you can access its elements by indexes like this:<\/p>\n\n\n\n
list[index]<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Lists are zero-based indexes. In other words, the first element has an index of 0, the second element has an index of 1, and so on.<\/p>\n\n\n\n
For example, the following shows how to access the first element of the\u00a0numbers<\/code>\u00a0list:<\/p>\n\n\n\n
numbers = [1, 3, 2, 7, 9, 4] print(numbers[0])<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
1<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
The\u00a0numbers[1]<\/code>\u00a0will return the second element from the list:<\/p>\n\n\n\n
numbers = [1, 3, 2, 7, 9, 4] print(numbers[1])<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
3<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
The negative index allows you to access elements starting from the end of the list.<\/p>\n\n\n\n
The\u00a0list[-1]<\/code>\u00a0returns the last element. The\u00a0list[-2]<\/code>\u00a0returns the second last element, and so on. For example:<\/p>\n\n\n\n
numbers = [1, 3, 2, 7, 9, 4] print(numbers[-1]) print(numbers[-2])<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
4 9<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Modifying, adding, and removing elements<\/h2>\n\n\n\n
A list is dynamic. It means that you can modify elements in the list, add new elements to the list, and remove elements from a list.<\/p>\n\n\n\n
1) Modifying elements in a list<\/h3>\n\n\n\n
To change an element, you assign a new value to it using this syntax:<\/p>\n\n\n\n
list[index] = new_value<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
The following example shows how to change the first element of the\u00a0numbers<\/code>\u00a0list to 10:<\/p>\n\n\n\n
numbers = [1, 3, 2, 7, 9, 4] numbers[0] = 10 print(numbers)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
[10, 3, 2, 7, 9, 4]<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
The following shows how to multiply the second element by 10:<\/p>\n\n\n\n
numbers = [1, 3, 2, 7, 9, 4] numbers[1] = numbers[1]*10 print(numbers) <\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
[1, 30, 2, 7, 9, 4]<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
And the following divides the third element by 2:<\/p>\n\n\n\n
numbers = [1, 3, 2, 7, 9, 4] numbers[2] \/= 2 print(numbers)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
[1, 3, 1.0, 7, 9, 4]<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
2) Adding elements to the list<\/h3>\n\n\n\n
The\u00a0append()<\/code>\u00a0method appends an element to the end of a list. For example:<\/p>\n\n\n\n
numbers = [1, 3, 2, 7, 9, 4] numbers.append(100) print(numbers)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
[1, 3, 2, 7, 9, 4, 100]<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
The insert()<\/code> method adds a new element at any position in the list.<\/p>\n\n\n\n
For example, the following inserts the number 100 at index 2 of the\u00a0numbers<\/code>\u00a0list:<\/p>\n\n\n\n
numbers = [1, 3, 2, 7, 9, 4] numbers.insert(2, 100) print(numbers)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
[1, 3, 100, 2, 7, 9, 4]<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
3) Removing elements from a list<\/h3>\n\n\n\n
The del<\/code> statement allows you to remove an element from a list by specifying the position of the element.<\/p>\n\n\n\n
The following example shows how to remove the first element from the list:<\/p>\n\n\n\n
numbers = [1, 3, 2, 7, 9, 4] del numbers[0] print(numbers)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
[3, 2, 7, 9, 4]<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
The\u00a0pop()<\/code>\u00a0method removes the last element from a list and returns that element:<\/p>\n\n\n\n
numbers = [1, 3, 2, 7, 9, 4] last = numbers.pop() print(last) print(numbers) <\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
4 [1, 3, 2, 7, 9]<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Typically, you use the pop()<\/code> method when you want to remove an element from a list and still want to access the value of that element.<\/p>\n\n\n\n
To pop an element by its position, you use the\u00a0pop()<\/code>\u00a0with the element\u2019s index. For example:<\/p>\n\n\n\n
numbers = [1, 3, 2, 7, 9, 4] second = numbers.pop(1) print(second) print(numbers)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
3 [1, 2, 7, 9, 4]<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
To remove an element by value, you use the remove()<\/code> method. Note that the remove()<\/code> method removes only the first element it encounters in the list.<\/p>\n\n\n\n
For example, the following removes the element with value 9 from the\u00a0numbers<\/code>\u00a0list:<\/p>\n\n\n\n
numbers = [1, 3, 2, 7, 9, 4, 9] numbers.remove(9) print(numbers)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
[1, 3, 2, 7, 4, 9]<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
In this example, the remove()<\/code> method removes only the first number 9 but it doesn\u2019t remove the second number 9 from the list.<\/p>\n","protected":false},"excerpt":{"rendered":"
Summary: in this tutorial, you\u2019ll learn about Python List type and how to manipulate list elements effectively. What is a List A list is an ordered collection of items. Python uses the square brackets ([]) to indicate a list. The following shows an empty list: Typically, a list contains one or more items. To separate […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[19],"tags":[],"class_list":["post-64","post","type-post","status-publish","format-standard","hentry","category-5-lists"],"_links":{"self":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/64","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/comments?post=64"}],"version-history":[{"count":1,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/64\/revisions"}],"predecessor-version":[{"id":65,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/64\/revisions\/65"}],"wp:attachment":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/media?parent=64"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/categories?post=64"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/tags?post=64"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}