有什么方法可以删除 Python 中的嵌套类？

Question

下面的脚本尝试从Outer 类中删除Inner1 嵌套类。我收到明确的错误“TypeError：无法删除 __class__ 属性”。死胡同？

def Loader(cls):
    for key in dir(cls):
        value = getattr(cls, key)
        if isinstance(value, type):
            delattr(cls, key)
    return cls

@Loader
class Outer:
    class Inner1:
        X = 1

print(Outer.Inner1.X)

Answer 1

问题在于以下行：

if isinstance(value, type):

匹配从type 继承的所有内容。如果您只想删除在装饰类中明确定义的内部类，您可以使用以下内容：

from inspect import isclass

def Loader(cls):
    # vars returns the __dict__ attributes, so only names that are explicitely defined in cls.
    for key, value in vars(cls).copy().items():

        # If it is a class, delete it
        if isclass(value):
            delattr(cls, key)

    return cls

@Loader
class Outer:
    class Inner1:
        X = 1

print(Outer.Inner1.X) # AttributeError: type object 'Outer' has no attribute 'Inner1'

另一种方法是将您的装饰器设为一个类，并明确告诉它您要删除的名称。例如

class Loader:
    def __init__(self, *args):
        # Store the given names to delete
        self.names = args

    def __call__(self, cls):
        for name in self.names:
            try:
                delattr(cls, name)
            except AttributeError:
                pass

        return cls

@Loader('Inner1', 'Inner2', 'etc')
class Outer:
    class Inner1:
        X = 1

print(Outer.Inner1.X) # AttributeError: type object 'Outer' has no attribute 'Inner1'

也就是说，我不确定您为什么要装饰一个类并定义您将动态删除的内部类...为什么不...根本不定义它们？ :D