的 classmethod()是Python中的内置函数，它为给定函数返回类方法。
用法： classmethod(function)
参数：该函数接受函数名称作为参数。
返回类型：该函数返回转换后的类方法。
classmethod()方法绑定到类而不是对象。类方法可以同时由类和对象调用。这些方法可以通过类或对象来调用。下面的示例清楚地说明了上面。
范例1：
# Python program to understand classmethod
class Student:
# creating a variable
name = "Geeksforgeeks"
# creating a function
def print_name(obj):
print("The name is:", obj.name)
# creating print_name classmethod
# before creating this line print_name()
# can be called only with object not with class
Student.print_name = classmethod(Student.print_name)
# now this method can be call as classmethod
# print_name() method is called as class method
Student.print_name()
输出：
The name is: Geeksforgeeks
范例2：
# Python program to understand classmethod
class Subject:
# creating a variable
favorite_subject = "Networking"
# creating a function
def favorite_subject_name(obj):
print("My favorite_subject_name is:",
obj.favorite_subject)
# creating favorite_subject_name classmethod
# before creating this line favorite_subject_name()
# can be called only with object not with class
Subject.favorite_subject_name = classmethod(Subject.favorite_subject_name)
# now this method can be call as classmethod
# favorite_subject_name() method is called as class method
Subject.favorite_subject_name()
输出：
My favorite_subject_name is: Networking
classmethod()的使用classmethod()函数用于工厂设计模式，在该模式下，我们想使用类名而不是对象来调用许多函数。
的@classmethod装饰器：
的@classmethod装饰器，是一个内置的函数装饰器，它是一个表达式，在定义函数后会对其求值。评估的结果使您的函数定义变得模糊。类方法将类作为隐式第一个参数接收，就像实例方法接收实例一样。
用法:
class C(object):
@classmethod
def fun(cls, arg1, arg2, ...):
....
fun: function that needs to be converted into a class method
returns: a class method for function.
- 类方法是绑定到类而不是类对象的方法。
- 他们可以访问类的状态，因为它需要一个指向该类而不是对象实例的类参数。
- 它可以修改适用于该类所有实例的类状态。例如，它可以修改将适用于所有实例的类变量。
在下面的示例中，我们使用staticmethod()和classmethod()检查一个人是否成年。
# Python program to demonstrate
# use of class method and static method.
from datetime import date
class Person:
def __init__(self, name, age):
self.name = name
self.age = age
# a class method to create a
# Person object by birth year.
@classmethod
def fromBirthYear(cls, name, year):
return cls(name, date.today().year - year)
# a static method to check if a
# Person is adult or not.
@staticmethod
def isAdult(age):
return age > 18
person1 = Person('mayank', 21)
person2 = Person.fromBirthYear('mayank', 1996)
print (person1.age)
print (person2.age)
# print the result
print (Person.isAdult(22))
输出：
21 22 True
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注：本文由纯净天空筛选整理自ankit15697大神的英文原创作品 classmethod() in Python。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。