3.4 Set Basics

• A set is an unordered collection of unique elements. Sets have the following properties:
  • Elements are unordered: Elements in the set do not have a position or index.
  • Elements are unique: No elements in the set share the same value.
• A set can be created using the set() function, which accepts a sequence-type iterable object (list, tuple, string, etc.)

• A set literal can be written using curly braces { } with commas separating set elements.

  • set literals execute twice as quickly

  

• an empty set can only be created using set()

• index operator is not valid cause the set is unordered and positions don't matter

# Initial list contains some duplicate values
first_names = [ 'Harry', 'Hermione', 'Ron', 'Harry', 'Albus', 'Ron', 'Ron' ]

# Creating a set removes any duplicate values
names_set = set(first_names)

print(names_set)

Modifying Sets

• Sets are mutable, elements can be added or removed.
• The add() method places a new element into the set if the set does not contain an element with the provided value.
  • set.add(value): Add value into the set. Ex: my_set.add('abc')
• The remove() and pop() methods remove an element from the set.
  • set.remove(value): Remove the element with given value from the set. Raises KeyError if value is not found. Ex: my_set.remove('abc')
  • set.pop(): Remove a random element from the set. Ex: my_set.pop()

Set operations