What is the purpose of the @classmethod decorator in Python?

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Answer:

The @classmethod decorator in Python is used to define a class method for a class. A class method is a method that is bound to the class and not the instance of the class. Class methods take the class itself as the first argument, conventionally named cls, rather than the instance of the class, conventionally named self. Class methods are useful for methods that operate on the class rather than on instances of the class.

The @classmethod decorator is used to indicate that a method should be a class method. A class method takes the class itself as the first argument, allowing it to access class-level data and methods.

For example, consider the following code:

class Person:
    people_count = 0

    def __init__(self, name):
        self.name = name
        Person.people_count += 1

    @classmethod
    def count_people(cls):
        return cls.people_count

In this example, the Person class defines a class method count_people, which returns the number of people that have been instantiated. The count_people method takes the class itself as the first argument, allowing it to access the class-level people_count attribute.

Class methods are called using the class name, rather than an instance of the class, as shown below:

num_people = Person.count_people()

By using the @classmethod decorator, the count_people method can access class-level data and methods, and can be called without creating an instance of the Person class. This makes the code more readable and maintainable, and helps to prevent programming errors by enforcing that this method operates on the class itself rather than on instances of the class.

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