元类基础

class SingletonMeta(type):
   _instances = {}
   
   def __call__(cls, *args, **kwargs):
       if cls not in cls._instances:
           cls._instances[cls] = super().__call__(*args, **kwargs)
       return cls._instances[cls]

class Singleton(metaclass=SingletonMeta):
   pass

类装饰器

def add_method(cls):
   def new_method(self):
       return "新方法"
   cls.new_method = new_method
   return cls

@add_method
class MyClass:
   pass

转载请注明：周志洋的博客 » Python进阶-元类编程