In Python, a set is an unordered collection with no duplicate elements.

We can create a set either using curly braces ({}) or the set() function.

Note: If we need to create an empty set, we need to use the set() function, not {}, because using curly braces will create a dictionary instead.

Creating sets

We can create a set from a list, string, tuple or dictionary, discarding any duplicate values.

A set from a string:

name = set("hemanta")

print(name)
# {'m', 'e', 't', 'h', 'n', 'a'}

Notice that there are two occurrences of the character a in the string hemanta. However there is only one a in the set. This is because a set can’t contain duplicate elements.

A set from a list:

js = ["React", "Node"]

js_set = set(js)

print(js_set)
# {'React', 'Node'}

A set from a tuple:

fashion_capital = ('Tokyo', 'Milan', 'London', 'Paris')

print(set(fashion_capital))
# {'Tokyo', 'London', 'Milan', 'Paris'}

A set from a dictionary:

portfolio = {'Google' : 'Google Pixel', 'Microsoft' : 'Microsoft Surface'}

print(set(portfolio))
# {'Microsoft', 'Google'}

Notice that the set is created only from the keys of the dictionary.

Counting items

We can count the number of items in a set using the len() function.

furniture = {'Ikea', 'Wayfair', 'Sears'}

print(len(furniture))
# 3

Adding items

We can add an item to a set using the add() method.

models = {'Alcazar', 'Elantra', 'Kona'}

models_portfolio = models.add('Tucson')

print(models)
# {'Alcazar', 'Elantra', 'Tucson', 'Kona'}

Deleting items

We can delete an item from a set using the remove() method.

models = {'Apple', 'Lenovo', 'Dell'}

models.remove('Dell')

print(models)
# {'Apple', 'Lenovo'}

Iterating over a set

We can iterate over all items in a set using a for...in loop.

models = {'Apple', 'OnePlus', 'Samsung'}

for brand in models:
    print(brand.upper(), end = " ")

# SAMSUNG APPLE ONEPLUS

Testing for a value

We can test whether an item is present in a set or not using the in operator.

models = {'MongoDB', 'Firebase', 'MySQL'}

print('PostGreSQL' in models)
# False

Learn about Python dictionaries & tuples in my blog post here & here respectively.