A set is another type of collection like list and tuple.

So what are sets?

Sets are unordered – Items stored in a set aren’t kept in any particular order.
Set items are unique – Duplicate items are not allowed.
Sets are unindexed – You cannot access set items by referring to an index.
Sets are changeable (mutable) – They can be changed in place, can grow and shrink on demand.

The values of a set are defined within curly braces { }.
A quick reminder:

For list, we use square brackets [ ].
For tuple, we use brackets ( ).

fruits = {'apple','orange'}
print(fruits);

Sets don't maintain order. Every time we execute the code, the order of the values in the set changes.

Do note, in the example below we are adding pineapple multi times, but when we print the set, we only see pineapple once. This is because set does not allow duplicate.

fruits = {'apple','orange'}
fruits.add('pineapple');
fruits.add('pineapple');
fruits.add('pineapple');
print(fruits);

Benefits of sets

The key benefit of sets is that they make comparing values between two sets easier.

Set Operations

Sets are commonly used for computing mathematical operations such as intersection, union, difference, and symmetric difference.

Difference

basket_1 = {"Strawberry", "Cherry", "Apple", "Grapes"}
basket_2 = {"Pear", "Avocado", "Lime", "Apple", "Grapes"}

# Difference  
basket_1_difference = basket_1.difference(basket_2);
basket_2_difference = basket_2.difference(basket_1);

print(basket_1_difference);
print(basket_2_difference);

Symmetric Difference

basket_1 = {"Strawberry", "Cherry", "Apple", "Grapes"}
basket_2 = {"Pear", "Avocado", "Lime", "Apple", "Grapes"}

# Symmetric Difference 
basket_1_symmetric_difference = basket_1.symmetric_difference(basket_2);
basket_2_symmetric_difference = basket_2.symmetric_difference(basket_1);
print(basket_1_symmetric_difference);
print(basket_2_symmetric_difference);

Intersection

basket_1 = {"Strawberry", "Cherry", "Apple", "Grapes"}
basket_2 = {"Pear", "Avocado", "Lime", "Apple", "Grapes"}

# Intersection
basket_1_intersection = basket_1.intersection(basket_2);
print(basket_1_intersection);

Union

basket_1 = {"Strawberry", "Cherry", "Apple", "Grapes"}
basket_2 = {"Pear", "Avocado", "Lime", "Apple", "Grapes"}

# Union
basket_1_union = basket_1.union(basket_2);
print(basket_1_union);

Learn Python: Sets