{"id":288,"date":"2020-10-06T03:39:37","date_gmt":"2020-10-06T03:39:37","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=288"},"modified":"2025-03-26T15:13:57","modified_gmt":"2025-03-26T15:13:57","slug":"python-sort-list","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/python-basics\/python-sort-list\/","title":{"rendered":"Python Sort List"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn how to use the Python List sort()<\/code> method to sort a list.<\/p>\n\n\n\n

Introduction to the Python List sort() method #<\/a><\/h2>\n\n\n\n

To sort a list<\/a>, you use the sort()<\/code> method:<\/p>\n\n\n

list.sort()<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The sort()<\/code> method sorts the original list in place. It means that the sort()<\/code> method modifies the order of elements in the list. <\/p>\n\n\n\n
By default, the sort()<\/code> method sorts the elements of a list using the less-than operator (<<\/code>).  In other words, it places the lower elements before the higher ones.<\/p>\n\n\n\n
To sort elements from higher to lower, you pass the reverse=True<\/code> argument to the sort()<\/code> method like this:<\/p>\n\n\n
list.sort(reverse=True<\/span>)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Sorting a list of strings #<\/a><\/h2>\n\n\n\n
If a list contains strings, the sort()<\/code> method sorts the string elements alphabetically. <\/p>\n\n\n\n
The following example uses the sort()<\/code> method to sort the elements in the guests<\/code> list alphabetically:<\/p>\n\n\n
guests = ['James'<\/span>, 'Mary'<\/span>, 'John'<\/span>, 'Patricia'<\/span>, 'Robert'<\/span>, 'Jennifer'<\/span>]\nguests.sort()\n\nprint(guests)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
['James'<\/span>, 'Jennifer'<\/span>, 'John'<\/span>, 'Mary'<\/span>, 'Patricia'<\/span>, 'Robert'<\/span>]<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
And the following example uses the sort()<\/code> method with the reverse=True<\/code> argument to sort the elements in the guests<\/code> list in the reverse alphabetical order:<\/p>\n\n\n
guests = ['James'<\/span>, 'Mary'<\/span>, 'John'<\/span>, 'Patricia'<\/span>, 'Robert'<\/span>, 'Jennifer'<\/span>]\nguests.sort(reverse=True<\/span>)\n\nprint(guests)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
['Robert'<\/span>, 'Patricia'<\/span>, 'Mary'<\/span>, 'John'<\/span>, 'Jennifer'<\/span>, 'James'<\/span>]<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Sorting a list of numbers #<\/a><\/h2>\n\n\n\n
If a list contains numbers, the sort()<\/code> method sorts the numbers from smallest to largest. <\/p>\n\n\n\n
The following example uses the sort()<\/code> method to sort numbers in the scores<\/code> list from smallest to largest:<\/p>\n\n\n
scores = [5<\/span>, 7<\/span>, 4<\/span>, 6<\/span>, 9<\/span>, 8<\/span>]\nscores.sort()\n\nprint(scores)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
[4<\/span>, 5<\/span>, 6<\/span>, 7<\/span>, 8<\/span>, 9<\/span>]<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
To sort numbers from the largest to smallest, you use the sort(reverse=True)<\/code> like this:<\/p>\n\n\n
scores = [5<\/span>, 7<\/span>, 4<\/span>, 6<\/span>, 9<\/span>, 8<\/span>]\nscores.sort(reverse=True<\/span>)\n\nprint(scores)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
[9<\/span>, 8<\/span>, 7<\/span>, 6<\/span>, 5<\/span>, 4<\/span>]<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Sorting a list of tuples #<\/a><\/h3>\n\n\n\n
Suppose that you have a list of  tuples like this:<\/p>\n\n\n
companies = [('Google'<\/span>, 2019<\/span>, 134.81<\/span>),\n             ('Apple'<\/span>, 2019<\/span>, 260.2<\/span>),\n             ('Facebook'<\/span>, 2019<\/span>, 70.7<\/span>)]<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
And you want to sort the companies list by revenue from highest to lowest. To do it:<\/p>\n\n\n\n
First, specify a sort key and pass it to the sort()<\/code> method. To define a sort key, you create a function that accepts a tuple and returns the element that you want to sort by:<\/p>\n\n\n
def<\/span> sort_key<\/span>(company)<\/span>:<\/span>\n    return<\/span> company[2<\/span>]<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
This sort_key()<\/code> function accepts a tuple called company<\/code> and returns the third element.<\/p>\n\n\n\n
Note that the company is a tuple e.g., ('Google', 2019, 134.81)<\/code>. And the company[2]<\/code> references the revenue like 134.81<\/code> in this case.<\/p>\n\n\n\n
Second, pass the sort_key function to the sort()<\/code> method:<\/p>\n\n\n
companies.sort(key=sort_key, reverse=True<\/span>)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The sort()<\/code> method will use the value returned by the sort_key()<\/code> function for the comparisons. <\/p>\n\n\n\n
Note that you just pass the function name without the parentheses to the sort()<\/code> method:<\/p>\n\n\n
companies = [('Google'<\/span>, 2019<\/span>, 134.81<\/span>),\n             ('Apple'<\/span>, 2019<\/span>, 260.2<\/span>),\n             ('Facebook'<\/span>, 2019<\/span>, 70.7<\/span>)]\n\n\n# define a sort key<\/span>\ndef<\/span> sort_key<\/span>(company)<\/span>:<\/span>\n    return<\/span> company[2<\/span>]\n\n\n\n# sort the companies by revenue<\/span>\ncompanies.sort(key=sort_key, reverse=True<\/span>)\n\n# show the sorted companies<\/span>\nprint(companies)\n<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
[('Apple'<\/span>, 2019<\/span>, 260.2<\/span>), ('Google'<\/span>, 2019<\/span>, 134.81<\/span>), ('Facebook'<\/span>, 2019<\/span>, 70.7<\/span>)]<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Using lambda expression #<\/a><\/h3>\n\n\n\n
To make it more concise, Python allows you to define a function without a name with the following syntax:<\/p>\n\n\n
lambda<\/span> arguments: expression<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Technically, it’s equivalent to the following function:<\/p>\n\n\n
def<\/span> name<\/span>(arguments)<\/span>:<\/span>\n    return<\/span> expression<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The following example uses the lambda expression to sort the companies by revenue from low to high:<\/p>\n\n\n
companies = [('Google'<\/span>, 2019<\/span>, 134.81<\/span>),\n             ('Apple'<\/span>, 2019<\/span>, 260.2<\/span>),\n             ('Facebook'<\/span>, 2019<\/span>, 70.7<\/span>)]\n\n# sort the companies by revenue<\/span>\ncompanies.sort(key=lambda<\/span> company: company[2<\/span>])\n\n# show the sorted companies<\/span>\nprint(companies)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
[('Facebook'<\/span>, 2019<\/span>, 70.7<\/span>), ('Google'<\/span>, 2019<\/span>, 134.81<\/span>), ('Apple'<\/span>, 2019<\/span>, 260.2<\/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
A function without a name is called an anonymous function<\/strong>. And this syntax is called a lambda expression<\/a><\/strong>. <\/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
Try it<\/a><\/p>\n\n\n\n