class User(父类):uid = ("uid", "int unsigned")name = ("username", "varchar(20)")password = ("password", "varchar(20)")...省略...

u = User(nid=12345, name="laowang",password="123321")

insert into (uid,name,password) value (12345,"laowang","123321")

class Mode_type(type):def __new__(cls, name, bases, attrs)mappings = dict()for k, v in attrs.items():if isinstanse(v, tuple):mappings[k] = v# 找到新字典接收完attrs的数据后，删掉attrs里的数据for k in mappings.keys[]:attrs.pop(k)# 将之前新字典保存的数据表的信息保存在attrs中attrs["__mappings__"] = mappings# name指向新创建的实例对象名，相当于保存数据表的名称attrs["__table__"] = name    return type.__new__(cls, name, bases, attrs)class User(mateclass = Mode_type):uid = ("uid", "int unsigned")name = ("username", "varchar(20)")password = ("password", "varchar(20)")#  指定元类后，以上的类属性就不在类中，而是在__mapping__指定的字典中仓储# 类似于# __mapping__ = {#        uid :("uid", "int unsigned")#        name: ("username", "varchar(20)")#        password :("password", "varchar(20)")# }# __table__ = "User"def __init__(self, **kwargs):# 取出字典里面的值for name, value in kwargs.items():setattr(self, name, value)# 这里不能用self.name = value ，这样只会让实例对象拥有name这个属性，而不是name形参背后真正替换的属性，所以用setattrdef save()# 数据表表头字段fields = []# 数据表字段对应的数据args = []for k, v in self.__mappings__.items():field.append(v[0])args.append(getattr(self, k, None))args_temp = list()# 区分参数的类型，防止写入数据表后报错for temp in args:if isinstence(temp, int):args_temp.append(str(temp))  # 类似temp = “123456”elif isinstence(temp, str)：args_temp.append("""%s""" % temp)  # 类似temp = """'123321'"""sql = "insert into %s (%s) value (%s)" % (self.__table__, ",".join(fields), ",".join(args_temp))#  下面就可以执行mysql的操作，只是说ORM，所以我只打印了这句话    print(sql)u = User(uid = 123456, name="laowang"， password = "123321"）
u.save()