1 说明

大多数情况，@classmethod和@staticmethod效果一样。但是如果有继承关系，情况有所不同。

2 @classmethod的真实意义

2.1 类生成例

#!/usr/bin/python
# -*- coding: UTF-8 -*-
 
class A(object):
    bar = 1
    def func1(self):  
        print ('foo') 
    @classmethod
    def func2(cls):
        print ('func2')
        print (cls.bar)
        cls().func1()   # 调用 foo 方法
 
A.func2()               # 不需要实例化

 2.1 @classmethod类工厂

from datetime import date

# random Person
class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    @classmethod
    def fromBirthYear(cls, name, birthYear):
        return cls(name, date.today().year - birthYear)

    def display(self):
        print(self.name + "'s age is: " + str(self.age))

person = Person('Adam', 19)
person.display()

person1 = Person.fromBirthYear('John',  1985)
person1.display()

3  @classmethod和@staticmethod的区别

假设您创建了 Foo 的子类并在子类上调用了 create_new 方法

class Bar(Foo):
    pass

obj = Bar.create_new()

然后这个基类将导致一个新的 Bar 对象被创建......

class Foo:
    @classmethod
    def create_new(cls):
        return cls()

而这个基类会导致创建一个新的 Foo 对象

class Foo:
    @staticmethod
    def create_new():
        return Foo()

采取哪一个？取决于你想要的行为。

from datetime import date

# random Person
class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    @staticmethod
    def fromFathersAge(name, fatherAge, fatherPersonAgeDiff):
        return Person(name, date.today().year - fatherAge + fatherPersonAgeDiff)

    @classmethod
    def fromBirthYear(cls, name, birthYear):
        return cls(name, date.today().year - birthYear)

    def display(self):
        print(self.name + "'s age is: " + str(self.age))

class Man(Person):
    sex = 'Male'

man = Man.fromBirthYear('John', 1985)
print(isinstance(man, Man))

man1 = Man.fromFathersAge('John', 1965, 20)
print(isinstance(man1, Man))