Implementation of class attributes and class methods in django

Django directly defines the properties of the class and can be called directly in instantiated objects or classes.

Class attributes:version_number is a class attribute that is shared among all instances. It is initialized when the class is loaded.

class Book:
    version_number = "1.0.0"

    def __init__(self, title, author):
         = title
         = author

    @classmethod
    def get_version(cls):
        return cls.version_number

#Use class methodsprint(Book.get_version())  # Output: 1.0.0

When do you need a class method?@classmethod）：

1. If you need to define a method, it needs to access class-level data (such as class properties);

2. Defining the class method is to have otherMethods other than this class can also be called。

3. If you need to define a method, you need to be in the methodUse cls to create an instance of a class

4. Perform other class-related operations, then you should use @classmethod.

class Book:
    version_number = "1.0.0"

    def __init__(self, title, author):
         = title
         = author

    @classmethod
    def get_version(cls):
        return cls.version_number

#Use class methodsprint(Book.get_version())  # Output: 1.0.0

In this example, get_version is a class method that is declared through the @classmethod decorator, allowing you to access the class property version_number. If your requirements are similar, then you need to use class methods. Otherwise, if you just need to execute a function at class definition and store the result as a class property, you don't need to define it as a class method.

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