Abstract Classes

Python Notes: ABC Module

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The ABC module in Python stands for Abstract Base Classes. It’s used to define interfaces for classes. This means you specify what methods a class must have, without specifying how those methods are implemented.

Key Concepts:

Abstract Base Classes (ABCs): These are classes that cannot be instantiated directly. They serve as blueprints for other classes. They define a common interface that subclasses must adhere to.
abstractmethod: A decorator used to mark methods within an ABC as abstract. Subclasses must provide implementations for these methods. If they don’t, a TypeError is raised at runtime.

Example:

from abc import ABC, abstractmethod

class Shape(ABC): # Declare Shape as an abstract base class
    @abstractmethod
    def area(self):
        pass  # Abstract method - no implementation needed here

    @abstractmethod
    def perimeter(self):
        pass # Abstract method - no implementation needed here

class Circle(Shape):
    def __init__(self, radius):
        self.radius = radius

    def area(self):
        return 3.14159 * self.radius * self.radius

    def perimeter(self):
        return 2 * 3.14159 * self.radius

class Rectangle(Shape):
    def __init__(self,width, height):
        self.width = width
        self.height = height
    
    def area(self):
        return self.width * self.height
    
    def perimeter(self):
        return 2*(self.width + self.height)

#This will raise a TypeError because Shape is an abstract class
#shape = Shape()

circle = Circle(5)
print(f"Circle Area: {circle.area()}")
print(f"Circle Perimeter: {circle.perimeter()}")

rectangle = Rectangle(4,6)
print(f"Rectangle Area: {rectangle.area()}")
print(f"Rectangle Perimeter: {rectangle.perimeter()}")

Related Notes:

Further points to consider:

Error Handling: How to handle situations where subclasses fail to implement required abstract methods.
Benefits of using ABCs: Improved code organization, maintainability, and extensibility. Enforcing a consistent interface across different classes.
Use Cases: Examples of when using ABCs is particularly beneficial (e.g., designing APIs, working with polymorphic behavior).

ABC Module

Carson West

Abstract Classes

Python Notes: ABC Module