Python Classes #

Classes provide a means of bundling data and functionality together. Creating a new class creates a new type of object, allowing new instances of that type to be made.

Defining a Class #

You can define a class using the class keyword.

class Dog:
 # Class attribute
 species = "Canis familiaris"
 # Initializer / Instance attributes
 def __init__(self, name, age):
 self.name = name
 self.age = age
 # Instance method
 def description(self):
 return f"{self.name} is {self.age} years old"
 # Another instance method
 def speak(self, sound):
 return f"{self.name} says {sound}"

Creating an Instance #

To create an instance of a class, you call the class as if it were a function.

# Create an instance of the Dog class
my_dog = Dog("Buddy", 5)
# Access instance attributes
print(my_dog.name) # Buddy
print(my_dog.age) # 5
# Call instance methods
print(my_dog.description()) # Buddy is 5 years old
print(my_dog.speak("Woof")) # Buddy says Woof

Inheritance #

Inheritance allows you to create a new class that inherits the attributes and methods of an existing class.

class Bulldog(Dog):
 def speak(self, sound="Arf"):
 return f"{self.name} says {sound}"
my_bulldog = Bulldog("Rocky", 3)
print(my_bulldog.description()) # Rocky is 3 years old
print(my_bulldog.speak()) # Rocky says Arf

Special Methods #

Classes in Python can implement special methods (also known as “dunder” methods) that begin and end with double underscores. These methods allow you to customize the behavior of your objects.

• __init__: The constructor for the class.
• __str__: Returns a string representation of the object.
• __len__: Returns the length of the object.
• __repr__: Returns an official string representation of the object.

class Car:
 def __init__(self, make, model):
 self.make = make
 self.model = model
 def __str__(self):
 return f"A {self.make} {self.model}"
my_car = Car("Toyota", "Corolla")
print(my_car) # A Toyota Corolla