Sets

Sets are like Lists, but they are unordered and they guarantee uniqueness. Only ONE of each value can be in a set.

fruits = {"apple", "banana", "grape"}
print(type(fruits))
# Prints: <class 'set'>

print(fruits)
# Prints: {'banana', 'grape', 'apple'}

Add Values

You can .add() values to a set. Think of .add() like append but for sets!

fruits = {"apple", "banana", "grape"}
fruits.add("pear")
print(fruits)
# Prints: {'pear', 'banana', 'grape', 'apple'}

No error will be raised if you add an item already in the set, and the set will remain unchanged.

An Empty Set

Because the empty bracket {} syntax creates an empty dictionary, to create an empty set, you need to use the set() function.

fruits = set()
fruits.add("pear")
print(fruits)
# Prints: {'pear'}

Set Iteration

fruits = {"apple", "banana", "grape"}
for fruit in fruits:
    print(fruit)
    # Prints:
    # banana
    # grape
    # apple

Note: Sets are unordered, so the order of iteration is not guaranteed.

Assignment

Complete the remove_duplicates function. It should take a list of spells that a player has learned and return a new List where there is at most one of each title. You can accomplish this in at least two ways:

Iteration:

Create a set to track spells that have been seen
Create a list to store the unique spells
Iterate over the list
1. If the spell is not in the set, add it to the set and the list
Return the list

Set conversion:

Convert the list to a set
Convert the set back to a list and return it.

It makes no sense to learn a spell twice! Once it's learned, it's learned forever.