Python classmethod()

通常要調用一個類的方法，我們需要首先創建該類的一個實例或對象。但是類方法綁定到類，而不是它的對象，所以類方法函數的創建返回給定函數的類方法

 **classmethod(function)** #where function is an name of function

classmethod()函數只接受一個參數

方法的返回值或輸出是類方法，可以在沒有類實例的情況下調用。

| 投入 | 返回值 |
| 功能 | 返回傳遞函數的類方法 |

 class Products:
getcode = 『P36』

def getProductCode(cls):
print('The Product Code is:', cls.getcode)

# create printCode class method
Products.getProductCode = classmethod(Products .getProductCode ) 
Products.getProductCode () 

輸出:

The Product Code is: P36 

 # 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))
 pers 19)
person.display()
 pers  1985)
person1.display() 

輸出:

Adam's age is: 19
John's age is: 31 

 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)) 

輸出:

True
False