https://www.v2ex.com/t/781645

meta_class.py

class Meta(type):
    def __new__(self, class_name, bases, attrs):
        print(attrs)
        return type(class_name, bases, attrs)

# 没有更高层级的类且与 Meta 处于同一模块时 Dog1 与 Dog2 等价
Dog1 = Meta('Dog', (), {'x': 5})

class Dog(metaclass=Meta):
    x = 5

Dog2 = Dog

# 存在更高层级的类时 Dog3 与 Dog4 不等价
class Toplevel:
    Dog3 = Meta('Dog', (), {'x': 5})
    
    class Dog(metaclass=Meta):
        x = 5

Dog3, Dog4 = Toplevel.Dog3, Topleve2.Dog

# __qualname__ 属性（限定名称）不相等
assert(Dog3.__qualname__ == 'Dog')
assert(Dog4.__qualname__ == 'Toplevel.Dog')
assert(Dog3.__qualname__ != Dog4.__qualname__)

other_class.py

# 另一个模块（文件）
from .meta_class import Meta

# 与 Meta 所处模块不同时 Dog5 与 Dog6 不等价
Dog5 = Meta('Dog', (), {'x': 5})

class Dog(metaclass=Meta):
    x = 5

Dog6 = Dog

# __module__ 属性（所属模块的名称）不相等
assert(Dog5.__module__ == 'meta_class')
assert(Dog6.__module__ == 'other_class')
assert(Dog5.__module__ != Dog6.__module__)