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Union() function in Python

  • Difficulty Level : Easy
  • Last Updated : 08 Oct, 2021

Python set Union() function returns a new set which contains all the items from the original set.

Union of two given sets is the smallest set which contains all the elements of both the sets. Union of two given sets A and B is a set which consists of all the elements of A and all the elements of B such that no element is repeated.

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The symbol for denoting union of sets is ‘U’ 

Examples: 

Input: Let set A = {2, 4, 5, 6} and set B = {4, 6, 7, 8}

Output: {2, 4, 5, 6, 7, 8} 

Explanation: Taking every element of both the sets A and B, without repeating any element, we get a new set = {2, 4, 5, 6, 7, 8}.This new set contains all the elements of set A and all the elements of set B with no repetition of elements and is named as union of set A and B.  

Python set Union() Syntax:

set1.union(set2, set3, set4….) 

In parameters, any number of sets can be given

 Python set Union() Return value:

The union() function returns a set, which has the union of all sets(set1, set2, set3…) with set1. It returns a copy of set1 only if no parameter is passed. 

Example of Python set Union() methods:

Example 1: Working with Python set Union() methods

Python3




# Python3 program for union() function
 
set1 = {2, 4, 5, 6}
set2 = {4, 6, 7, 8}
set3 = {7, 8, 9, 10}
 
# union of two sets
print("set1 U set2 : ", set1.union(set2))
 
# union of three sets
print("set1 U set2 U set3 :", set1.union(set2, set3))

Output: 

set1 U set2 :  {2, 4, 5, 6, 7, 8}
set1 U set2 U set3 : {2, 4, 5, 6, 7, 8, 9, 10}

Example 2: Set Union Using the | Operator

We can use “|” operator to find the union of the sets.

Python3




# Python3 program for union with | operator
 
set1 = {2, 4, 5, 6}
set2 = {4, 6, 7, 8}
set3 = {7, 8, 9, 10}
 
# union of two sets
print("set1 U set2 : ", set1 | set2)
 
# union of three sets
print("set1 U set2 U set3 :", set1 |set2 | set3)

Output:

set1 U set2 :  {2, 4, 5, 6, 7, 8}
set1 U set2 U set3 : {2, 4, 5, 6, 7, 8, 9, 10}



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