Python Set

Python Set

Introduction to Python – Set

A set is an unordered collection of elements. Every element is unique (no duplicate values in set) and are immutable (i.e. values cannot be changed). However, the set itself is mutable which means we can add or remove elements from set.

Sets is very useful to perform mathematical set operations like union and intersection.

Create a Python Set

A set is created by placing all the elements within curly braces { } and each elements separated by comma.

Set can have any number of elements with different data types like integer, float, string etc.

Example of set of an integers

>>> set1 = {1, 2, 3}
>>>set1
{1, 2, 3}

# set of mixed data types
>>>set2 = {101, "K Patel", 90.5}
>>>print(set2)
{'K Patel', 90.5, 101}

Set removes duplicate entries and arranges elements in order.

>>> set3 = {1,3,2,5,4,3}
>>> set3
{1, 2, 3, 4, 5}

Observe the following code:
>>> set2[0]
Traceback (most recent call last):
File "<pyshell#8>", line 1, in <module>
set2[0]
TypeError: 'set' object is not subscriptable

Note: 'set' object does not support indexing in python. We can’t access an element of set using indexing or slicing concept.

Changing Python Set Elements

Add() method can be used to add single element in to a set.

>>> set4 = {3, 5, 7}
>>> set4
{3, 5, 7}

>>> set4.add(6)
>>> set4
{3, 5, 6, 7}

Removing elements from Set

>>> set4.remove(7)
>>> set4
{3, 5, 6}

Note: Trying to remove element which does not exists in set will result in error. Observe the following code:

>>> set4(2)
Traceback (most recent call last):
File "<pyshell#15>", line 1, in <module>
set4(2)
TypeError: 'set' object is not callable

Python Set Operations - Union and Intersection

Python sets can be used to perform mathematical set operations like union and intersection.

Python Set Union

Union of Set A and Set B is a set of all elements from both the python sets. Union operation can be performed using union operator( | ) or the method union().

>>> set5 = {2, 4, 6, 8}
>>> set6 = {6, 8, 10, 12}
>>> set5.union(set6)
{2, 4, 6, 8, 10, 12}

>>> print(set5 | set6)
{2, 4, 6, 8, 10, 12}

Python Set Intersection

Intersection of Set A and Set B is a set of elements that are common in both sets. Python intersection can be performed using intersection operator ( & ) or using the method intersection().

>>> set5 & set6
{8, 6}

>>> set5.intersection(set6)
{8, 6}

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