{"id":613,"date":"2020-10-17T09:39:17","date_gmt":"2020-10-17T09:39:17","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=613"},"modified":"2025-03-27T03:04:55","modified_gmt":"2025-03-27T03:04:55","slug":"python-set-difference","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/python-basics\/python-set-difference\/","title":{"rendered":"Python Set Difference"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn about the Python Set difference and how to use it to find the difference between two or more sets.<\/p>\n\n\n\n

Introduction to the Python Set difference #<\/a><\/h2>\n\n\n\n

The difference between the two sets<\/a> results in a new set that has elements from the first set which aren’t present in the second set.<\/p>\n\n\n\n

Suppose you have the following s1<\/code> and s2<\/code> sets:<\/p>\n\n\n

s1 = {'Python'<\/span>, 'Java'<\/span>, 'C++'<\/span>}\ns2 = {'C#'<\/span>, 'Java'<\/span>, 'C++'<\/span>}<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
The difference between s1<\/code> and s2<\/code> sets results in the following set with one element:<\/p>\n\n\n
{'Python'<\/span>}\n<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
…because there is only 'Python'<\/code> element from the first set that doesn’t exist in the second set.<\/p>\n\n\n\n
The set difference isn’t commutative. The difference between the s2<\/code> and s1<\/code> sets returns the following set:<\/p>\n\n\n
{'C#'<\/span>}<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
The following Venn diagram illustrates the difference between the s1<\/code> and s2<\/code> sets:<\/p>\n\n\n\n
\"Python<\/figure>\n\n\n\n
And the following Venn diagram illustrates the difference between s2<\/code> and s1<\/code> sets:<\/p>\n\n\n\n
\"Python<\/figure>\n\n\n\n
In Python, you can use the set difference()<\/code> method or set difference operator (-<\/code>) to find the difference between sets.<\/p>\n\n\n\n
1) Using Python Set difference() method to find the difference between sets #<\/a><\/h3>\n\n\n\n
The Set<\/code> type has a difference()<\/code> method that returns the difference between two or more sets:<\/p>\n\n\n
set1<\/span>.difference<\/span>(s2<\/span>, s3<\/span>, ...)<\/code><\/span>Code language:<\/span> CSS<\/span> (<\/span>css<\/span>)<\/span><\/small><\/pre>\n\n\n
For example, you can use the set difference()<\/code> method to find the difference between s1<\/code> and s2<\/code> sets:<\/p>\n\n\n
s1 = {'Python'<\/span>, 'Java'<\/span>, 'C++'<\/span>}\ns2 = {'C#'<\/span>, 'Java'<\/span>, 'C++'<\/span>}\ns = s1.difference(s2)\n\nprint<\/span>(s)<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
{'Python'<\/span>}<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
And this example shows how to use the set difference()<\/code> method to find the difference between s2<\/code> and s1<\/code> sets.<\/p>\n\n\n
s1 = {'Python'<\/span>, 'Java'<\/span>, 'C++'<\/span>}\ns2 = {'C#'<\/span>, 'Java'<\/span>, 'C++'<\/span>}\ns = s2.difference(s1)\n\nprint<\/span>(s)<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
{'C#'<\/span>}<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
Note that the difference()<\/code> method returns a new set. It doesn’t change the original sets.<\/p>\n\n\n\n
2) Using Python set difference operator (-) to find the difference between sets #<\/a><\/h3>\n\n\n\n
Besides the difference()<\/code> method, Python provides you with the set difference operator (-<\/code>) that allows you to find the difference between sets.<\/p>\n\n\n
s = s1 - s2<\/code><\/span><\/pre>\n\n\n
The following example uses the difference operator (-<\/code>) to find the difference between the s1<\/code> and s2<\/code> sets:<\/p>\n\n\n
s1 = {'Python'<\/span>, 'Java'<\/span>, 'C++'<\/span>}\ns2 = {'C#'<\/span>, 'Java'<\/span>, 'C++'<\/span>}\ns = s1 - s2\n\nprint<\/span>(s)<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
And this example use the set difference operator to return the difference between s2<\/code> and s1<\/code>:<\/p>\n\n\n
s1 = {'Python'<\/span>, 'Java'<\/span>, 'C++'<\/span>}\ns2 = {'C#'<\/span>, 'Java'<\/span>, 'C++'<\/span>}\ns = s2 - s1\n\nprint<\/span>(s)<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
{'C#'<\/span>}<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
The set difference() method vs set difference operator (-) #<\/a><\/h3>\n\n\n\n
The set difference()<\/code> method can accept one or more iterables<\/a> (e.g., strings<\/a>, lists<\/a>, dictionaries<\/a>) while the set difference operator (-<\/code>) only allows sets.<\/p>\n\n\n\n
When you pass iterables to the set difference()<\/code> method, it’ll convert the iterables to sets before performing the difference operation.<\/p>\n\n\n\n
The following shows how to use the set difference()<\/code> method with a list:<\/p>\n\n\n
scores = {7<\/span>, 8<\/span>, 9<\/span>}\nnumbers = [9<\/span>, 10<\/span>]\nnew_scores = scores.difference(numbers)\n\nprint<\/span>(new_scores)<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
However, if you use the set difference operator (-<\/code>) with iterables, you’ll get an error:<\/p>\n\n\n
scores = {7<\/span>, 8<\/span>, 9<\/span>}\nnumbers = [9<\/span>, 10<\/span>]\nnew_scores = scores - numbers\n\nprint<\/span>(new_scores)<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Error:<\/p>\n\n\n
TypeError<\/span>: unsupported operand type(s) for<\/span> -: 'set'<\/span> and 'list'<\/span><\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/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
Try it<\/a><\/strong><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n