Constructors

Special Methods

These are methods in Python classes that begin and end with double underscores (__), also known as “dunder” methods. They define how objects of the class behave in certain contexts. They’re crucial for creating classes that interact seamlessly with built-in Python features and other libraries.

Examples and Functionality:

• __init__(self, ...): The constructor. Called when you create an instance of the class. Used for initializing attributes.

class Dog:
    def __init__(self, name, breed):
        self.name = name
        self.breed = breed

my_dog = Dog("Buddy", "Golden Retriever")

• __str__(self): Defines how the object is represented as a string (using str(my_dog)). Crucial for readability.

class Dog:
    # ... __init__ ...
    def __str__(self):
        return f"Dog named {self.name}, breed: {self.breed}"

print(my_dog) # Calls __str__

• __repr__(self): Defines how the object is represented unambiguously (using repr(my_dog)). Intended for developers; should be unambiguous and ideally allow recreating the object.

class Dog:
    # ... __init__ ... __str__ ...
    def __repr__(self):
        return f"Dog('{self.name}', '{self.breed}')"

print(repr(my_dog)) # Calls __repr__

• __len__(self): Defines the length of the object (using len(my_object)). Useful for custom sequence-like classes.

class MyList:
    def __init__(self, data):
        self.data = data
    def __len__(self):
        return len(self.data)

my_list = MyList(1,2,3)
print(len(my_list))

• __add__(self, other): Defines the behavior of the + operator for objects of your class. Operator Overloading

• __eq__(self, other): Defines the behavior of the == operator. Operator Overloading

• __iter__(self): Makes your class iterable (using for loops). Needs to return an iterator object. Iterators and Generators

• __getitem__(self, key): Allows accessing items using indexing (my_object[index]]). Context Managers

Further Exploration:

• Operator Overloading: Focuses on __add__, __eq__, __mul__, etc. How to customize arithmetic and comparison Operators.
• Iterators and Generators: Detailed explanation of how to create iterable classes using __iter__ and __next__.
• Context Managers: Explanation of __enter__ and __exit__ methods for managing resources.
• Object Lifecycle: A deeper dive into object creation, destruction, and garbage collection. How these special methods interact with the Python interpreter.

This is not an exhaustive list, but covers some of the most frequently used special methods. The Python documentation provides a complete reference.