Day33.定制元类控制类的产生

1.定制元类控制类的产生_类People继承类Mymeta

'''如何自定义元类(type)来控制类的产生'''

# todo metaclass=type：代表继承原有的元类type
# class People(metaclass=type):

# todo metaclass=Mymeta：代表继承自定义的元类Mymeta
class Mymeta(type):     # 只有继承了type类的类才是元类
    #     4个传参：空对象, 'People', (object,), {...}
    def __init__(self, x, y, z):
        print('run....')
        print(self)
        print(x)
        print(y)
        print(z)


# People = Mymeta(class_name, class_bases, class_dic)
# People = Mymeta('People', (object,), {...})

# 调用Mymeta发生的三件事
# 1. 先造一个空对象 ==> People
# 2. 调用Mymeta这个类内的__init__方法，完成初始化对象的操作
# 3. 返回初始化好的对象

class People(object, metaclass=Mymeta):
    def __init__(self, name, age):
        self.name = name
        self.age = age
    
    def say(self):
        print('{}:{}'.format(self.name, self.age))

2.定制元类控制类的产生_判断People类名开头是否是大写字母

'''如何自定义元类(type)来控制类的产生'''

# todo metaclass=type：代表继承原有的元类type
# class People(metaclass=type):

# todo metaclass=Mymeta：代表继承自定义的元类Mymeta
class Mymeta(type):     # 只有继承了type类的类才是元类
    #     4个传参：空对象, 'People', (object,), {...}
    def __init__(self, x, y, z):
        # todo .istitle()判断调用的类名开头是否是大写字母
        if not x.istitle():
            # todo 类程序抛出异常
            raise NameError('类名字的首字母必须大写')

# People = Mymeta(class_name, class_bases, class_dic)
# People = Mymeta('People', (object,), {...})

# 调用Mymeta发生的三件事
# 1. 先造一个空对象 ==> People
# 2. 调用Mymeta这个类内的__init__方法，完成初始化对象的操作
# 3. 返回初始化好的对象

# class People(object, metaclass=Mymeta):
class people(object, metaclass=Mymeta):
    def __init__(self, name, age):
        self.name = name
        self.age = age
    
    def say(self):
        print('{}:{}'.format(self.name, self.age))