Constructors, Interfaces, and Memory

While Python has some similarities to other languages regarding these concepts, it also has some unique approaches.

Constructors

  • In Python: Unlike Java or C++, Python doesn't have a designated constructor keyword. Instead, it uses a special method called __init__(double underscore init) that gets called automatically whenever you create an object from a class.
  • Purpose: Similar to other languages, __init__ is used to initialize the object's attributes (data) with starting values. You can define parameters within __init__ to accept arguments during object creation and assign them to the object's attributes.

Interfaces

  • Python and Interfaces: Unlike some other object-oriented languages, Python doesn't have a formal concept of interfaces. However, it achieves similar functionality using abstract base classes (ABCs) from the abc module.
  • Abstract Base Classes (ABCs): An ABC defines the desired methods and their signatures that subclasses (classes inheriting from the ABC) must implement. This enforces a certain behavior for classes that derive from the ABC.

Memory

  • Object Creation: When you create an object in Python, memory is allocated to store the object's attributes and potentially its methods. Python's garbage collector automatically manages memory, freeing unused objects when they are no longer referenced.
  • Important Note: Unlike some languages with manual memory management, you don't need to explicitly deallocate memory in Python.

Here's an example that combines these concepts:

Python
from abc import ABC, abstractmethod

class Shape(ABC):
  @abstractmethod
  def area(self):
    pass  # This method must be implemented by subclasses

class Square(Shape):
  def __init__(self, side_length):
    self.side_length = side_length

  def area(self):
    return self.side_length * self.side_length

# Here, Square implements the required method from the Shape ABC
square = Square(5)
print(square.area())  # Output: 25

In this example, Shape is an ABC that defines an abstract method area. The Square class inherits from Shape and implements the area method to calculate the area of a square. When you create a Square object, memory is allocated for its side_length attribute and the methods it inherits from Shape.