Descriptor Property

Implement a custom descriptor that validates integer assignments.

descriptors oop python-advanced

Implement a descriptor class `PositiveInt` that, when used as a class attribute, validates that the assigned value is an integer greater than zero. The descriptor should raise `TypeError` if the assigned value is not an integer, and `ValueError` if it is an integer but less than or equal to zero. Accessing the attribute should return the stored value. Deleting the attribute should delete the stored value using `del`.

Define the class `PositiveInt` exactly as follows:

```python
class PositiveInt:
    def __init__(self):
        # store per-instance data here
        pass
    def __get__(self, obj, objtype=None):
        # implement
        pass
    def __set__(self, obj, value):
        # implement
        pass
    def __delete__(self, obj):
        # implement
        pass
```

Your implementation must support the following usage:

```python
class Person:
    age = PositiveInt()
    def __init__(self, age):
        self.age = age
```

- Assigning `age = 25` works.
- Assigning `age = 3.14` raises `TypeError`.
- Assigning `age = 0` raises `ValueError`.
- Accessing `person.age` returns the stored integer.
- Deleting `del person.age` makes subsequent access raise `AttributeError`.

Write the `PositiveInt` class only. Do not modify the `Person` example.

Constraints

The descriptor must be per-instance (no data sharing between instances).
The value stored must be exactly the integer provided.
The descriptor must handle `__get__` with `obj=None` gracefully (should return the descriptor itself).
Complexity: constant time operations.

Example

>>> class Person:
...     age = PositiveInt()
...     def __init__(self, age):
...         self.age = age
>>> p = Person(25)
>>> p.age
25
>>> p.age = 0
Traceback (most recent call last):
ValueError: age must be greater than zero
>>> p.age = 3.14
Traceback (most recent call last):
TypeError: age must be an integer
>>> del p.age
>>> p.age
Traceback (most recent call last):
AttributeError: 'Person' object has no attribute 'age'

20 points ~20 min

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Hints

Store values in a dictionary on the descriptor instance, keyed by the owner object (using `id(obj)` or the object itself).

In `__set__`, first check `type(value) is int` (not `isinstance` to reject booleans) and raise `TypeError` otherwise.

If the value is an integer but `value <= 0`, raise `ValueError`.

In `__get__`, if `obj is None` return the descriptor itself, otherwise retrieve from the dictionary or raise `AttributeError`.

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