As we mentioned earlier, the property descriptor is a mechanism for triggering function calls while accessing the attributes of an object.

In our example, they wrap access to the internal attributes with a leading underscore, like so:

contact.first_name = "John" # Stores "John" in contact._first_name
print(contact.first_name)   # Reads "John" from contact._first_name
contact.last_name = ""      # ValueError raised by the required function

The property descriptor is typically used with the @decorated syntax—remember to always use the same name for the decorated functions:

    @property
    def last_name(self):
        # ...

    @last_name.setter
    def last_name(self, value):
        # ...