Python Set

Python Set is like a dictionary, an unordered collection of keys, held without any values. The set type is mutable , the contents can be changed using methods like add() and remove() . Sets do not contain duplicates, every element in a Python set can have only one occurrence in that particular set, no multiple occurrences are allowed. There are currently two built-in set types, Set and Frozenset .

example

 
set_num = set("Hello World!")
print(set_num)

output

 
{'o', 'H', 'r', 'l', ' ', 'd', 'e', '!', 'W'}

Create a Set from Tuple

example

 
set_dir = set(('East','West','North','South'))
print(set_dir)

output

 
{'West', 'South', 'North', 'East'}

Create a Set from List

example

 
set_dir = set(['East','West','North','South'])
print(set_dir)

output

 
{'South', 'West', 'North', 'East'}

Sets are Mutable

The set type is mutable, the contents can be changed using methods like add() and remove().

example

 
set_col = set({'Red','Blue','Green'})
print(set_col)
set_col.add('White')
print(set_col)

output

 
{'Green', 'Blue', 'Red'}
{'White', 'Green', 'Blue', 'Red'}

Set.remove() remove elements from set.

example

 
set_col = set({'Red','Blue','Green'})
print(set_col)
set_col.remove('Blue')
print(set_col)

output

 
{'Blue', 'Green', 'Red'}
{'Green', 'Red'}

Set Length

len() function returned the length of a set.

example

 
set_col = set({'Red','Blue','Green'})
print(len(set_col))

output

3

Union of Sets

In Python, Union operation can be performed on two Python sets using the operator or by using the method union(). Union of two sets x and y is another set that contains all distinct elements in sets x and x.

Using | Operator

example

 
x = set({1,2,3,4,5})
y = set({3,4,5,6,7})
z = x  y
print(z)

output

 
{1, 2, 3, 4, 5, 6, 7}

Using union()

example

 
x = set({1,2,3,4,5})
y = set({3,4,5,6,7})
z = x.union(y)
print(z)

output

 
{1, 2, 3, 4, 5, 6, 7}

Intersection of Sets

In Python, Union operation can be performed on two Python sets using the operator & or by using the method intersection(). Intersection of two sets x and y is another set of elements those are present in both sets x and y (common to both of them).

Using & operator

example

 
x = set({1,2,3,4,5})
y = set({3,4,5,6,7})
z = x & y
print(z)

output

 
{3, 4, 5}

Using intersection()

example

 
x = set({1,2,3,4,5})
y = set({3,4,5,6,7})
z = x.intersection(y)
print(z)

output

 
{3, 4, 5}

Difference of Sets

The difference() method returns the set difference of two sets. In Python, Difference operation can be performed on two Python sets using the operator - or by using the method difference().

Using - operator

example

 
x = set({1,2,3,4,5})
y = set({3,4,5,6,7})
z = x-y
print(z)

output

 
{1, 2}

Using difference()

example

 
x = set({1,2,3,4,5})
y = set({3,4,5,6,7})
z = x.difference(y)
print(z)

output

 
{1, 2}

Symmetric Difference of Sets

Symmetric difference of the sets is the set of elements those are not common to both the sets. The symmetric_difference() method using.

Using symmetric_difference()

example

 
x = set({1,2,3,4,5})
y = set({3,4,5,6,7})
z = x.symmetric_difference(y)
print(z)

output

 
{1, 2, 6, 7}

Frozenset

A frozenset value is immutable: it's set up with the frozenset() function call, but once it's set up its contents cannot be altered.

example

 
set_col = frozenset({'Red','Blue','Green'})
print(set_col)
set_col.add('White')
print(set_col)

output

 
frozenset({'Blue', 'Red', 'Green'})
Traceback (most recent call last):
  File "sample.py", line 5, in < module >
    set_col.add('White')
AttributeError: 'frozenset' object has no attribute 'add'

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