自定义元类控制类的创建

# Chinese每次创建由原来的type改为Mymeta，因此可以在Mymeta内对类进行一些特殊定制

# 示例一：类名的大小写强控
#
# class Mymeta(type):
#     def __init__(self,class_name,class_bases,class_dic):
#         if not class_name.istitle():
#             raise TypeError('类名的首字母必须大写！')
#         super(Mymeta,self).__init__(class_name,class_bases,class_dic)


# class Chinese(object,metaclass=Mymeta):
#
#     country = 'China'
#
#     def __init__(self,name,age):
#         self.name = name
#         self.age = age
#
#     def talk(self):
#         print('%s is talking' % self.name)


# 示例二：注释强控

class Mymeta(type):
    def __init__(self,class_name,class_bases,class_dic):
        if '__doc__' not in class_dic or not class_dic['__doc__'].strip():
            raise TypeError('必须有注释，且注释不能为空！')
        super(Mymeta,self).__init__(class_name,class_bases,class_dic)

class Foo(object,metaclass=Mymeta):
    '''
    注释
    '''
    pass