Python Sets

Python sets are a data structure in Python that are not indexed or ordered, and are written with curly brackets ( { } ).  Python sets offer a major advantage of being a highly optimized method for validating whether an element is within in the set. The hash table is the base for the data structure.

Python Sets Methods

Python Set Creation

Creating a list in Python is easy by using curly brackets and surrounding the values with quotes if needed.

Input:

car_models = {"Mustang", "Camaro", "Civic", "Jetta"}

print(car_models)

Output:

{'Jetta', 'Camaro', 'Mustang', 'Civic'}

Python Set Access

Python does not allow access to items in a set by referring to an index. The reason is because sets are not ordered and there’s no index. However, one can use a for loop to access items by name, which will be discussed in this tutorial later.

Python Set Looping

As stated with Python sets access, in order to locate a item,  a for loop can print out each item that is in the set.

Input:

for x in car_models:
    print(f"Car model: {x} ")

Output:

Car model: Mustang 
Car model: Camaro 
Car model: Civic 
Car model: Jetta

Python Sets Validating Item

Python set item validating will determine if an item is in the list by using the keyword, in.

if…else Example 1

Input:

if "Gallardo" in car_models:
    print("Yes, Gallardo is in the list.")
else:
    print("No, Gallardo is not in the list.")

Output:

No, Gallardo is not in the list.

if…else Example 2

Input:

if "Mustang" in car_models:
    print("Yes, Mustang is in the list.")
else:
    print("No, Mustang is not in the list.")

Output:

Yes, Mustang is in the list.

Python Set Length

The internal method, len() will determine the length (item count)  of a set.

Input:

print(len(car_models))

Output:

4

Python Adding Set Item

The internal methods, add() will add a specified item to the end of a set.

Input:

car_models.add("Gallardo")

print(f"Gallardo is added to the car model set: {car_models} ")

Output:

Gallardo is added to the car model set: {'Camaro', 'Jetta', 'Gallardo', 'Mustang', 'Civic'}

Python Update Set Item

The internal method, update() will add a item to the index number specified.

Input:

car_models.update(["Mustang", "Camaro", "Civic", "Jetta", "M3"])

print(f"M3 is added to the car model set: {car_models} ")

Output:

M3 is added to the car model set: {'M3', 'Camaro', 'Jetta', 'Mustang', 'Civic', 'Gallardo'}

Python Set Item Removal

There are two methods to remove an item from a set . Below are the two methods:

• remove()
• discard()

remove()

The method remove() will remove the specified item in a string.

Input:

car_models.remove("Civic")

print(f"Civic is removed from the set: {car_models} ")

Output:

Civic is removed from the set: {'M3', 'Gallardo', 'Mustang', 'Jetta', 'Camaro'}

discard()

The method discard() will remove the specified item in a string.

Input:

car_models.discard("Mustang")

print(f"Mustang is discarded from the set: {car_models} ")

Output:

Mustang is discarded from the set: {'M3', 'Gallardo', 'Jetta', 'Camaro'}

Python set() Constructor

The set() constructor method to create a new set.

Input:

new_car_model_set = set(("Mustang", "Camaro", "Civic", "Jetta", "M3", "Lamborghini", "California", "Enzo"))

print(f"New car model set using the set() constructor method: {new_car_model_set} ")

Output:

New car model set using the set() constructor method: {'Enzo', 'California', 'M3', 'Jetta', 'Camaro', 'Mustang', 'Lamborghini', 'Civic'}