Sets

In python, a set is a data structure that stores an unordered collection of unique elements. The elements of a set must be immutable and hashable, and cannot be repeated. Sets are useful for performing mathematical operations on sets, such as union, intersection and difference, and for removing duplicates from a list.

Creating a set

Let’s create some sets of fruits

set.py

# List of fruits
set1 = {'apple', 'banana', 'pear'}
set2 = {'pear', 'grape', 'mango'}
print(set1)
print(set2)

Output:

terminal

{'apple', 'banana', 'pear'}
{'pear', 'grape', 'mango'}

Adding elements

To add an element to a set, you can use the .add() method.

set.py

# List of fruits
set1 = {'apple', 'banana', 'pear'}
set2 = {'pear', 'grape', 'mango'}

# Add elements to a set

set1.add('strawberry')
set2.add('guava')

print(set1)
print(set2)

Output:

terminal

{'apple', 'banana', 'pear', 'strawberry'}
{'pear', 'grape', 'mango', 'guava'}

Deleting an element

To delete an element from a set, you can use the .remove() method.

set.py

# List of fruits
set1 = {'apple', 'banana', 'pear'}
set2 = {'pear', 'grape', 'mango'}

# Delete elements from a set

set1.remove('pear')
set2.remove('mango')

print(set1)
print(set2)

Output:

terminal

{'apple', 'banana'}
{'pear', 'grape'}

Note

You can use discard() to not generate error if it doesn’t exist

Set Unions

You can join the elements of a set using the .union() function

set.py

# List of fruits
set1 = {'apple', 'banana', 'pear'}
set2 = {'pear', 'grape', 'mango'}

# Adding elements to a set

unions = set1.union(set2)

print(unions)

Output:

terminal

{'apple', 'banana', 'pear', 'grape', 'mango'}

Set Intersections

You can extract the elements that are repeated between sets using the .intersection() function

set.py

# List of fruits
set1 = {'apple', 'banana', 'pear'}
set2 = {'pear', 'grape', 'mango'}

# Adding elements to a set

intersection = set1.intersection(set2)

print(intersection)

Output:

terminal

{'pear'}

Set differences

You can obtain the elements that are in one set but not in another using the .difference() function. This is useful for identifying which values are exclusive to a set.

set.py

# List of fruits
set1 = {'apple', 'banana', 'pear'}
set2 = {'pear', 'grape', 'mango'}

# Adding elements to a set

difference = set1.difference(set2)

print(difference)

Output:

terminal

{'apple', 'banana'}

Set Functions

Function	Description
copy()	Creates a copy of the set.
clear()	Removes all elements from the set.
isdisjoint()	Checks if two sets are disjoint (have no common elements).
issuperset()	Checks if a set is a subset of another.
symmetric_difference()	Returns the symmetric difference between two sets.
update()	Modifies the original set by adding elements from another set.
intersection_update()	Modifies the original set to contain only elements in common with another set.
difference_update()	Modifies the original set to contain only elements that are not in another set.
symmetric_difference_update()	Modifies the original set to contain only elements that are not in both sets.