The Set union() method returns a new set containing all unique elements from two or more sets.
Syntax
my_set.union(set1, set2, ...)union() Parameters
Python Set union() method parameters:
| Parameter | Condition | Description |
|---|---|---|
set1, set2, ... |
Optional | A comma-separated list of one or more sets to merge with |
union() Return Value
Python Set union() method returns a new set with elements from the set and all other sets passed as argument.
Example
Example 1: Union of Two Sets with union() method
A = {'Tom', 'Anna'}
B = {'David', 'Ryan'}
result = A.union(B)
print(result) # Output: {'Ryan', 'Anna', 'Tom', 'David'}output
{'Ryan', 'Anna', 'Tom', 'David'}Example 2: Union between Multiple Sets
The union() method allows to compute the union of elements from multiple sets:
A = {1, 2, 3}
B = {3, 4, 5, 6, 7}
C = {6, 7, 8, 9, 10}
result = A.union(B, C)
print(result) # Output: {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}output
{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}Example 3: Shallow Copy with union()
When called without any arguments, union() returns a new set that contains all the elements of the original set.
This behavior is effectively a shallow copy operation because it duplicates the set without creating a deep copy of the elements themselves.
original_set = {1, 2, 3}
shallow_copy = original_set.union()
original_set.add(4)
print("Original Set:", original_set) # Output: Original Set: {1, 2, 3, 4}
print("Shallow Copy:", shallow_copy) # Output: Shallow Copy: {1, 2, 3}output
Original Set: {1, 2, 3, 4}
Shallow Copy: {1, 2, 3}Example 4: Union between a Set and a List
You can also pass iterables like list: union() first converts the iterables to sets and then computes the union.
For example:
A = {'a', 'e', 'i', 'o', 'u'}
B = ['d', 'e', 'f']
result = A.union(B)
print(result) # Output: {'a', 'i', 'u', 'f', 'e', 'd', 'o'}output
{'a', 'i', 'u', 'f', 'e', 'd', 'o'}Example 5: Union between a Set and a Tuple
You can also pass iterables like tuple: union() first converts the iterables to sets and then computes the union.
For example:
A = {'a', 'e', 'i', 'o', 'u'}
B = ('d', 'e', 'f')
result = A.union(B)
print(result) # Output: {'a', 'i', 'u', 'f', 'e', 'd', 'o'}output
{'a', 'i', 'u', 'f', 'e', 'd', 'o'}Example 6: Union between a Set and a Dictionary
You can also pass iterables like dictionary: union() first converts the iterables to sets and then computes the union.
For example:
A = {'a', 'e', 'i', 'o', 'u'}
B = {1: 'd', 2: 'e', 3: 'f'}
C = {'d': 1, 'e': 2, 'f': 3}
print(A.union(B)) # Output: {'u', 1, 2, 3, 'a', 'e', 'o', 'i'}
print(A.union(C)) # Output: {'u', 'd', 'f', 'a', 'e', 'o', 'i'}output
{'u', 1, 2, 3, 'a', 'e', 'o', 'i'}
{'u', 'd', 'f', 'a', 'e', 'o', 'i'}Example 7: Union between a Set and a String
You can also pass iterables like string: union() first converts the iterables to sets and then computes the union.
For example:
A = {'a', 'e', 'i', 'o', 'u'}
B = 'def'
print(A.union(B)) # Output: {'a', 'i', 'u', 'f', 'e', 'd', 'o'}output
{'a', 'i', 'u', 'f', 'e', 'd', 'o'}Equivalent Operator | for union()
Set Union can be performed with the | operator as well, providing an alternative to the union() method.
A = {1, 2, 3, 4, 5}
B = {3, 4, 5, 6, 7}
result = A | B
print(result) # Output: {1, 2, 3, 4, 5, 6, 7}output
{1, 2, 3, 4, 5, 6, 7}Moreover, you can use the | operator with multiple sets:
A = {1, 2, 3}
B = {3, 4, 5, 6, 7}
C = {6, 7, 8, 9, 10}
result = A | B | C
print(result) # Output: {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}output
{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}