Why is the `self` Parameter Mandatory in Python Methods?

Understanding the Purpose and Necessity of self in Python Methods

In Python, class methods typically include the self parameter, which raises questions about its purpose and necessity. To shed light on this, let's consider the following example:

class MyClass:
    def func(self, name):
        self.name = name

It is understood that self represents the instance of MyClass on which the method func is called. However, the question arises: why is it mandatory to explicitly declare self in the parameter list, and why must it be used within the method's code?

Design Principle: Explicit Instance Attribution

Unlike many other languages that implicitly handle instance attribution, Python follows a principle of explicitness. This means that all references to instance attributes must be explicitly qualified with the instance to which they belong. In the context of methods, this responsibility falls upon the self parameter.

In the example above, when calling func with my_object, the self parameter will automatically contain a reference to my_object. By using self.name, the method can directly manipulate the name attribute of the specific instance being operated on.

Method Declaration and Invocation

Python treats methods as functions, with the sole difference being the first parameter. When a method is invoked, the instance is automatically passed as the first argument, enabling the method to access and modify the instance's attributes. This design allows for seamless integration of objects and their methods.

Any other parameter passed to the method will be treated separately from self. For instance, func(self, name) indicates that the self parameter represents the instance, while name is an additional input argument.

Conclusion

The self parameter in Python methods serves as an explicit reference to the instance on which the method is invoked. This design choice aligns with Python's principle of explicitness and enables methods to manipulate instance attributes directly.

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