Python – Find union of multiple sets

• Last Updated : 02 Feb, 2021

Given multiple sets list, the task is to write a Python program to find union of each set.

Examples:

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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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