Sets

Just like a list, a set is a collection of items. The difference between a set and a list is that a set cannot contain duplicates. So, if you have 5 chocolates and you put them in a set, you’ll only be left with 1 chocolate as duplicates will be removed. 😢

In the image above, the left side represents Indoor Games (Chess & Table Tennis) while the right side represents the Outdoor Games (Cricket & Football). The middle represents the common part of both these sets. These are the games that can be played Indoors as well as Outdoors (Basketball & Badminton). The middle part is also known as the intersection between two sets.

indoorGames = set(["Chess", "Table Tennis", "Basketball", "Badminton"])
outdoorGames = {"Cricket", "Football", "Basketball", "Badminton"}
print('** Indoor Games **')
print(indoorGames)
print('** Outdoor Games **')
print(outdoorGames)

Output

** Indoor Games **
set(["Chess", "Table Tennis", "Basketball", "Badminton"])
** Outdoor Games **
set(["Cricket", "Football", "Basketball", "Badminton"])

Union of Sets

If we have 2 sets as above, the union of these two sets contains the games from both the sets. The output will be a new set. The duplicates will be removed.

The symbol used for Union is |.

allGames = indoorGames | outdoorGames
print('** All Games **')
print(allGames)

Output

** All Games **
set(["Chess", "Table Tennis", "Basketball", "Badminton", "Cricket", "Football"])

Intersection of Sets

The intersection of 2 sets will be the set containing both indoor and outdoor games.

The symbol used for Intersection is &.

commonGames = indoorGames & outdoorGames
print('** Common Games **')
print(commonGames)

Output

** Common Games **
set(["Basketball", "Badminton"])

Difference of Sets

The difference of 2 sets will be the set that contains games from one set that are not present in the other set.

The symbol used for Difference is -.

indoorOnlyGames = indoorGames - outdoorGames
print('** Indoor Only Games **')
print(indoorOnlyGames)

Output

** Indoor Only Games **
set(["Chess", "Table Tennis"])

Print the items of a set

You cannot print the items of a set using the item number like a list. The elements of a set are not in a fixed sequence.

Therefore, you cannot do something like indoorGames[0], or indoorGames[1] like you can do in a list. However, you can go through the elements of a set using a for loop.

for g in indoorGames:
  print(g)

Output

Chess
Table Tennis
Basketball
Badminton

Adding items to a set

We can use the .add function to add a new game to a set.

indoorGames.add("Carrom")
print('** Indoor Games **')
print(indoorGames)

Output

** Indoor Games **
set(["Chess", "Table Tennis", "Basketball", "Badminton", "Carrom"])

Removing items to a set

We can use the .discard function to remove an item from the set.

indoorGames.discard("Chess")
print('** Indoor Games **')
print(indoorGames)

Output

** Indoor Games **
set(["Table Tennis", "Basketball", "Badminton", "Carrom"])

Try it Yourself