Explain the differences between self and cls in the context of class methods.

In Python, self and cls are conventions for the first parameter of methods, but they serve different purposes:

• self is a reference to a specific instance of the class. It is used in instance methods to access attributes and methods of that object.
• cls is a reference to the class itself, not an instance. It is used in class methods (marked with the @classmethod decorator) to work with the class as a whole, for example, to create new instances or modify class properties.

Example:

class MyClass:
    class_var = 0

    def __init__(self, value):
        self.instance_var = value

    def instance_method(self):
        print(f'Instance var: {self.instance_var}')

    @classmethod
    def class_method(cls):
        print(f'Class var: {cls.class_var}')

obj = MyClass(10)
obj.instance_method()  # calls the instance method
MyClass.class_method()  # calls the class method