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 listtest_list = [{4, 3, 5, 2}, {8, 4, 7, 2}, {1, 2, 3, 4}, {9, 5, 3, 7}]# printing original listprint("The original list is : " + str(test_list))# * operator packs sets for unionres = set().union(*test_list)# printing resultprint("Multiple set union : " + str(res)) |
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}
Time Complexity: O(n*m) where n is the number of sets in the test_list and m is the average number of elements in each set.
Auxiliary Space: O(m), where m is the average number of elements in each set. This is because the program creates a new set, that has the union of all the elements in the sets in test_list, and the space occupied by this set is m.
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() + * operatorfrom itertools import chain# initializing listtest_list = [{4, 3, 5, 2}, {8, 4, 7, 2}, {1, 2, 3, 4}, {9, 5, 3, 7}]# printing original listprint("The original list is : " + str(test_list))# * operator packs sets for unionres = set(chain(*test_list))# printing resultprint("Multiple set union : " + str(res)) |
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 #3 : Using Counter() function
Python3
# Python3 code to demonstrate working of# Union multiple setsfrom collections import Counterfrom itertools import chain# initializing listtest_list = [{4, 3, 5, 2}, {8, 4, 7, 2}, {1, 2, 3, 4}, {9, 5, 3, 7}]# printing original listprint("The original list is : " + str(test_list))# * operator packs sets for unionres = list(Counter(chain(*test_list)).keys())res.sort()# printing resultprint("Multiple set union : " + str(list(res))) |
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]
Time Complexity: O(n)
Auxiliary Space: O(n)
Method #4: Using update() method
Python3
# Python3 code to demonstrate working of# Union multiple sets# initializing listtest_list = [{4, 3, 5, 2}, {8, 4, 7, 2}, {1, 2, 3, 4}, {9, 5, 3, 7}]# printing original listprint("The original list is : " + str(test_list))res=set()for i in test_list: res.update(i)# printing resultprint("Multiple set union : " + str(list(res))) |
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]
Time Complexity: O(n)
Auxiliary Space: O(1)
Method #5: Using reduce() method:
Python3
# Using reduce() function from functools modulefrom functools import reduce# Initializing list of setstest_list = [{4, 3, 5, 2}, {8, 4, 7, 2}, {1, 2, 3, 4}, {9, 5, 3, 7}]# Printing original list of setsprint("The original list is : " + str(test_list))# Using reduce() function to obtain union of multiple setsres = reduce(set.union, test_list)# Printing resultprint("Multiple set union : " + str(res))#This is contributed by Jyothi pinjala |
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}
Time Complexity: O(n)
Auxiliary Space: O(n)
Method #6: Using set.update() method
Python3
# initialize the list of setstest_list = [{4, 3, 5, 2}, {8, 4, 7, 2}, {1, 2, 3, 4}, {9, 5, 3, 7}]# Printing original list of setsprint("The original list is : " + str(test_list))# create an empty set to store the unionresult = set()# use set.update() method to find the unionfor s in test_list: result.update(s)# print the resultprint("The union of multiple sets:", result)#This code is contributed by Vinay Pinjala |
The original list is : [{2, 3, 4, 5}, {8, 2, 4, 7}, {1, 2, 3, 4}, {9, 3, 5, 7}]
The union of multiple sets: {1, 2, 3, 4, 5, 7, 8, 9}
Time Complexity: O(n)
Auxiliary Space: O(n)
