python使用classmethod爲多個構造函數

Question

我一直在努力嘗試用classmethod裝飾器創建多個構造函數。有一個在SO一個例子 - What is a clean, pythonic way to have multiple constructors in Python?（第二個答案）

class Cheese(object): 
    def __init__(self, num_holes=0): 
     "defaults to a solid cheese" 
     self.number_of_holes = num_holes 

    @classmethod 
    def random(cls): 
     return cls(random(100)) 

    @classmethod 
    def slightly_holey(cls): 
    return cls(random(33)) 

    @classmethod 
    def very_holey(cls): 
     return cls(random(66, 100)) 

但是這個例子不是很清晰，代碼不會對我在Python 3鍵入命令給予時不起作用：

gouda = Cheese() 
emmentaler = Cheese.random() 
leerdammer = Cheese.slightly_holey() 

給 -

AttributeError: type object 'Cheese' has no attribute 'random' 

因爲這是我能找到的唯一例子之一。

Answer 1

randint應該工作：

from random import randint 

class Cheese(object): 
    def __init__(self, num_holes=0): 
     "defaults to a solid cheese" 
     self.number_of_holes = num_holes 

    @classmethod 
    def random(cls): 
     return cls(randint(0, 100)) 

    @classmethod 
    def slightly_holey(cls): 
     return cls(randint(0, 33)) 

    @classmethod 
    def very_holey(cls): 
     return cls(randint(66, 100)) 

gouda = Cheese() 
emmentaler = Cheese.random() 
leerdammer = Cheese.slightly_holey() 

現在：

>>> leerdammer.number_of_holes 
11 
>>> gouda.number_of_holes 
0 
>>> emmentaler.number_of_holes 
95