A set is an unordered collection with no duplicate elements.
basket = {'apple', 'orange', 'apple', 'pear', 'orange', 'banana'}
print(sorted(basket))['apple', 'banana', 'orange', 'pear']
Curly braces or the set() function can be used to create sets.
print(set('abracadabra') == {'a', 'r', 'b', 'c', 'd'})True
Note: to create an empty set you have to use set(), not ; the latter creates an empty dictionary
empty_set = set()
empty_dict = {}
print(type(empty_set))
print(type(empty_dict))<class 'set'> <class 'dict'>
Because sets are unordered, iterating over them or printing them can produce the elements in a different order than you expect.
my_set = {'apple', 'banana', 'cherry'}
print(my_set[0])TypeError
s = {'apple'}
s.add('banana')
print(sorted(s))['apple', 'banana']
Set objects also support mathematical operations like union, intersection, difference, and symmetric difference.
a = {'a', 'r', 'b', 'c', 'd'}
b = {'a', 'l', 'c', 'z', 'm'}
print(sorted(a - b))You can create an empty set using {}.
{} creates an empty dictionary. You must use set(). — {} creates an empty dictionary. You must use set().
Sets keep their items in the order you inserted them.
Sets are completely unordered collections. — Sets are completely unordered collections.
You can access the first item in a set using my_set[0].
Sets are not sequences; they do not support indexing. — Sets are not sequences; they do not support indexing.
Sets can contain lists or dictionaries.
Set elements must be hashable, meaning they cannot be mutable objects like lists or dictionaries. — Set elements must be hashable, meaning they cannot be mutable objects like lists or dictionaries.
Write a function 'unique_names' that takes a list of names and returns a new list with all duplicates removed, sorted alphabetically.
Convert the list to a set to remove duplicates, then back to a list, and finally use sorted().
def unique_names(names):
return sorted(list(set(names)))
print(unique_names(['Alice', 'Bob', 'Alice', 'Charlie']))Write a function 'common_interests' that takes two lists of hobbies and returns a sorted list of the hobbies present in both.
Convert both lists to sets, use the & operator to find the intersection, then return a sorted list.
def common_interests(list1, list2):
return sorted(list(set(list1) & set(list2)))
print(common_interests(['reading', 'coding', 'hiking'], ['hiking', 'swimming', 'coding']))