Why do Python classes inherit object?

In Python, every class you create inherits from a special class known as an object. This foundational element simplifies and empowers Python programming. When a new class is defined without specifying a superclass, Python assumes that it inherits from the object class. This is referred to as a "new-style" class declaration and was introduced in Python 2.2. Let’s explore why this is so important through explanations and code examples.

Inheritance from object Provides Essential Features

Inheriting from object grants classes several essential features and behaviors:

• __class__ Attribute: Each object has a __class__ attribute that points to its class. This attribute is part of the object model provided by the object class.
• Method Resolution Order (MRO): The object class is involved in the method resolution order, which determines the order in which base classes are searched when looking up a method. This helps in the resolution of method calls in complex inheritance hierarchies.
• __repr__, __str__, and Other Methods: The object class provides default implementations for methods like __repr__, __str__, __eq__, and __hash__. These methods can be overridden by subclasses to customize their behavior.
• __init__ Method: The object class has a default __init__ method that initializes new instances. Subclasses can override this method to provide custom initialization behavior.

Compatibility with New Style Classes

Before Python 2.2, Python had two types of classes: old-style and new-style. Old-style classes did not inherit from object, while new-style classes did. New-style classes, which are defined by inheriting from object, introduced several important features, such as:

• Descriptors: Mechanisms for managing attribute access and setting.
• Metaclasses: Classes of classes that define how classes themselves are created.
• Super(): A built-in function for calling methods from a parent class, which supports multiple inheritance more effectively.

Examples

Example 1: The following code checks whether an instance of MyExampleClass is also an instance of the object, which it is, demonstrating the inherent uniformity.

class MyExampleClass:
    pass

# Instance of MyExampleClass
example = MyExampleClass()
print(isinstance(example, object))

Output:

True

Example 2: The __init__ method is a special method in Python classes known as the constructor. It is called automatically when an instance of the class is created. This method initializes the attributes of the class. The __str__ method is another special method in Python. It defines the string representation of an object. When the print() function is called on an instance of the class, the __str__ method is executed to provide a human-readable string representation of the object.

class Book:
    def __init__(self, title):
        self.title = title

    def __str__(self):
        return "Book: " + self.title


book = Book("Learn Python")
print(book)

Output:

Book: Learn Python

Conclusions

Inheriting from object provides uniformity, consistency, and access to advanced features like MRO, descriptors, and properties. Understanding this inheritance helps us appreciate the robust object-oriented features in Python and the evolution from old-style to new-style classes. As Python continues to evolve, these foundational concepts remain crucial for writing efficient and maintainable code.