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Python – Find union of multiple sets

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  • Last Updated : 02 Feb, 2021
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Given multiple sets list, the task is to write a Python program to find union of each set.

Examples:

Input : test_list = [{4, 3, 5, 2}, {8, 4, 7, 2}, {1, 2, 3, 4}, {9, 5, 3, 7}]

Output : {1, 2, 3, 4, 5, 7, 8, 9}

Explanation : All elements from all sets included. Duplicates removed.

Input : test_list = [{4, 3, 5, 2}, {8, 4, 7, 2}, {1, 2, 3, 4}]

Output : {1, 2, 3, 4, 5, 7, 8}

Explanation : All elements from all sets included. Duplicates removed.

Method #1 : Using union() + * operator

In this, we perform task of getting union using union(), and * operator is used to perform task of packing all the sets together.

Python3




# Python3 code to demonstrate working of
# Union multiple sets
# Using union() + * operator
  
# initializing list
test_list = [{4, 3, 5, 2}, {8, 4, 7, 2}, {1, 2, 3, 4}, {9, 5, 3, 7}]
  
# printing original list
print("The original list is : " + str(test_list))
  
# * operator packs sets for union
res = set().union(*test_list)
  
# printing result
print("Multiple set union : " + str(res))

Output:

The original list is : [{2, 3, 4, 5}, {8, 2, 4, 7}, {1, 2, 3, 4}, {9, 3, 5, 7}]

Multiple set union : {1, 2, 3, 4, 5, 7, 8, 9}

Method #2 : Using chain.from_iterable() + * operator

In this, we perform task of union, which in turn is flattening using from_iterable().

Python3




# Python3 code to demonstrate working of
# Union multiple sets
# Using chain.from_iterable() + * operator
from itertools import chain
  
# initializing list
test_list = [{4, 3, 5, 2}, {8, 4, 7, 2}, {1, 2, 3, 4}, {9, 5, 3, 7}]
  
# printing original list
print("The original list is : " + str(test_list))
  
# * operator packs sets for union
res = set(chain(*test_list))
  
# printing result
print("Multiple set union : " + str(res))

Output:

The original list is : [{2, 3, 4, 5}, {8, 2, 4, 7}, {1, 2, 3, 4}, {9, 3, 5, 7}]

Multiple set union : {1, 2, 3, 4, 5, 7, 8, 9}


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