Python: What is a property vs descriptor?

1# property — simple getter/setter
2class Circle:
3    def __init__(self, radius):
4        self._radius = radius
5
6    @property
7    def radius(self):
8        return self._radius
9
10    @radius.setter
11    def radius(self, value):
12        if value < 0:
13            raise ValueError("Radius must be positive")
14        self._radius = value
15
16    @property
17    def area(self):
18        return 3.14 * self._radius ** 2
19
20# Custom descriptor — reusable validation
21class Validated:
22    def __init__(self, min_value=None, max_value=None):
23        self.min_value = min_value
24        self.max_value = max_value
25
26    def __set_name__(self, owner, name):
27        self.name = name
28
29    def __get__(self, obj, objtype=None):
30        if obj is None:
31            return self
32        return obj.__dict__.get(self.name)
33
34    def __set__(self, obj, value):
35        if self.min_value is not None and value < self.min_value:
36            raise ValueError(f"{self.name} must be >= {self.min_value}")
37        if self.max_value is not None and value > self.max_value:
38            raise ValueError(f"{self.name} must be <= {self.max_value}")
39        obj.__dict__[self.name] = value
40
41class Product:
42    price = Validated(min_value=0)
43    quantity = Validated(min_value=0, max_value=1000)
44
45p = Product()
46p.price = 100    # OK
47# p.price = -10  # ValueError!