Python 3.x 如何将元类应用于我的所有类，而不在类声明中硬编码它

为了考试，教授让我写一个元类，在项目中的所有类上生效，而不直接在类声明中声明它，这是可能的吗？怎样？ 例如，我有以下代码：

class MetaOne(type): 
    def __new__(meta, classname, supers, classdict):
        print('In MetaOne.new: ', classname, supers, classdict, sep='\n...') 
        return type.__new__(meta, classname, supers, classdict) 
    def __init__(Class, classname, supers, classdict): 
        print('In MetaOne init:', classname, supers, classdict, sep='\n...') 
        print('...init class object:', list(Class.__dict__.keys()))

class Eggs: pass 

print('making class') 

class Spam(Eggs): 
    data = 1 
    def meth(self, arg): pass 

print('making instance') 
X = Spam() 
print('data:', X.data)

class MetaOne(type): 
    def __new__(meta, classname, supers, classdict):
        print('In MetaOne.new: ', classname, supers, classdict, sep='\n...') 
        return type.__new__(meta, classname, supers, classdict) 
    def __init__(Class, classname, supers, classdict): 
        print('In MetaOne init:', classname, supers, classdict, sep='\n...') 
        print('...init class object:', list(Class.__dict__.keys()))

class Eggs: pass 

print('making class') 

class Spam(Eggs, metaclass=MetaOne): 
    data = 1 
    def meth(self, arg): pass 

print('making instance') 
X = Spam() 
print('data:', X.data)

我希望输出等于以下代码的输出：

class MetaOne(type): 
    def __new__(meta, classname, supers, classdict):
        print('In MetaOne.new: ', classname, supers, classdict, sep='\n...') 
        return type.__new__(meta, classname, supers, classdict) 
    def __init__(Class, classname, supers, classdict): 
        print('In MetaOne init:', classname, supers, classdict, sep='\n...') 
        print('...init class object:', list(Class.__dict__.keys()))

class Eggs: pass 

print('making class') 

class Spam(Eggs): 
    data = 1 
    def meth(self, arg): pass 

print('making instance') 
X = Spam() 
print('data:', X.data)

class MetaOne(type): 
    def __new__(meta, classname, supers, classdict):
        print('In MetaOne.new: ', classname, supers, classdict, sep='\n...') 
        return type.__new__(meta, classname, supers, classdict) 
    def __init__(Class, classname, supers, classdict): 
        print('In MetaOne init:', classname, supers, classdict, sep='\n...') 
        print('...init class object:', list(Class.__dict__.keys()))

class Eggs: pass 

print('making class') 

class Spam(Eggs, metaclass=MetaOne): 
    data = 1 
    def meth(self, arg): pass 

print('making instance') 
X = Spam() 
print('data:', X.data)

元类将应用于我的所有类，即使我没有直接声明它。

---

我有很多关于元类的问题，但最后在他们的类定义中总是使用元类=元声明。

好吧，我很难理解你的问题

如果

Eggs

继承

MetaOne

和

Spam

继承

Eggs

，这是否完成了您要做的事情

示例#1： 示例2： 您可能会用到网站上提供的信息，尤其是前面链接中的以下代码块：

class FilterClass(type):
    @classmethod
    def __prepare__(name, bases, **kwds):
        return collections.OrderedDict()

    def __new__(metacls, name, bases, namespace, **kwds):
        result = type.__new__(metacls, name, bases, dict(namespace))
        result._filters = [
            value for value in namespace.values() if hasattr(value, '_filter')]
        return result

这段代码演示了如何在不使用

metaclass=ABCMeta

的情况下创建元类

示例#3： 您是否熟悉

super（）

---

在这个用例中，

Spam

、

Scrambled

和

Fried

的元类都将是

MetaOne
您可以在模块级编写
\uuuuuuuu元类=您的\uu元类
。下面定义的所有类都将使用该元类。如果在类定义中再次编写
\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu=type
，则可以覆盖此项。子类正在使用父类的元类。
Eggs不继承MetaOneYes，在您的代码中不继承。如果是这样，
Spam
只需要继承
Eggs
，问题是让元类工作，而不在类声明中写入metaclass=ABCMeta谢谢，这个答案很好，现在我试图解决我的考试，然后我告诉你我使用了哪种方法。
class MetaOne: pass

class Eggs: pass

__metaclass__ = MetaOne

class Spam: pass
class Scrambled: pass
class Fried: pass