数据模型的类型的约束

基于描述符建立数据模型实现赋值验证框架

在实例属性的获取和设定方面，前面已经提过可以使用property和描述符实现

1、创建数据模型的基础构建模块

 1 class Descriptor:
 2     def __init__(self, name=None, **opts):
 3         self.name = name
 4         for key, val in opts.items():
 5             setattr(self, key, val)
 6 
 7     def __set__(self, instance, value):
 8         instance.__dict__[self.name] = value
 9 
10 
11 class Typed(Descriptor):
12     expected_type = type(None)
13 
14     def __set__(self, instance, value):
15         if not isinstance(value, self.expected_type):
16             raise TypeError("expect:{}".format(self.expected_type))
17         super().__set__(instance, value)
18 
19 
20 class Unsigned(Descriptor):
21     def __set__(self, instance, value):
22         if value < 0:
23             raise ValueError("expect > 0")
24         super().__set__(instance, value)

接着

2、定义不同的数据类型

 1 class Interger(Typed):
 2     expected_type = int
 3 
 4 
 5 class Float(Typed):
 6     expected_type = float
 7 
 8 
 9 class String(Typed):
10     expected_type = str

接着

3、介入类装饰器

 1 def check_attributes(**kwargs):
 2     def decorate(cls):
 3         for key, value in kwargs.items():
 4             if isinstance(value, Descriptor):
 5                 value.name = key
 6                 setattr(cls, key, value)
 7             else:
 8                 setattr(cls, key, value(key))
 9         return cls
10 
11     return decorate

最后

4、应用

 1 @check_attributes(
 2     name=String,
 3     age=Interger
 4 )
 5 class Valley:
 6 
 7     def __init__(self):
 8         self.name = "g"
 9         self.age = 26
10 
11 
12 if __name__ == '__main__':
13     print(Valley().__dict__)

整合

 1 class Descriptor:
 2     def __init__(self, name=None, **opts):
 3         self.name = name
 4         for key, val in opts.items():
 5             setattr(self, key, val)
 6 
 7     def __set__(self, instance, value):
 8         instance.__dict__[self.name] = value
 9 
10 
11 class Typed(Descriptor):
12     expected_type = type(None)
13 
14     def __set__(self, instance, value):
15         if not isinstance(value, self.expected_type):
16             raise TypeError("expect:{}".format(self.expected_type))
17         super().__set__(instance, value)
18 
19 
20 class Unsigned(Descriptor):
21     def __set__(self, instance, value):
22         if value < 0:
23             raise ValueError("expect > 0")
24         super().__set__(instance, value)
25 
26 
27 class Interger(Typed):
28     expected_type = int
29 
30 
31 class Float(Typed):
32     expected_type = float
33 
34 
35 class String(Typed):
36     expected_type = str
37 
38 
39 def check_attributes(**kwargs):
40     def decorate(cls):
41         for key, value in kwargs.items():
42             if isinstance(value, Descriptor):
43                 value.name = key
44                 setattr(cls, key, value)
45             else:
46                 setattr(cls, key, value(key))
47         return cls
48 
49     return decorate
50 
51 
52 @check_attributes(
53     name=String,
54     age=Interger
55 )
56 class Valley:
57 
58     def __init__(self):
59         self.name = "g"
60         self.age = 26
61 
62 
63 if __name__ == '__main__':
64     print(Valley().__dict__)

这一块还是要好好琢磨琢磨