One of the hidden gems in Python classes are seamless getters and setters. I discovered this through the book [Effective Python by Brett Slatkin](https://effectivepython.com/). Though the example I'll use is different and shorter than the one he uses in his book.
Let's create a class representing a person. The only information we're going to store is their age and we'll make it optional to provide it.
```python
class Person:
def __init__(self, age=None):
self._age = None
@property
def age(self):
if self._age is None:
raise ValueError("age must be set before accessing it.")
return self._age
@age.setter
def age(self, age):
if age <0:
raise ValueError("age must be at least zero.")
self._age = age
```
The second function in the class decorated by `@property` will be the getter function for the attribute `_age`. The name of the function will be what we expect the user to access it as. The setter is then decorated with `age.setter` where `age` is the name of the attribute. As such the name chosen in the getter function name, setter function name, and decorator must all match.
Now let's try using it
```python
bobby = Person()
bobby.age
```
```
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/user/test.py", line 7, in age
raise ValueError("age must first be set before accessing it")
ValueError: age must first be set before accessing it
