When should you use a property instead of explicit getter and setter methods?

Short answer

A property exposes a computed or validated value through plain attribute syntax, and you can start with a simple attribute and turn it into a property later without breaking the interface.

Explanation

In Python there is no need to write getX and setX up front as in Java; start with a public attribute and, when you need validation or computation, convert it into a property. A property is a descriptor at its core. Reading it should stay cheap and free of surprising side effects; if it performs I/O or heavy computation, it is clearer as an explicit method, or use functools.cached_property for expensive values that do not change.

Code example

class Account:
    def __init__(self, balance: int):
        self.balance = balance  # Passes through setter

    @property
    def balance(self) -> int:
        return self._balance

    @balance.setter
    def balance(self, value: int) -> None:
        if value < 0:
            raise ValueError("balance cannot be negative")
        self._balance = value

Common mistakes

• Running a database query inside a property that is called in loops without noticing.
• Writing getters and setters for every field without need, as in Java.

Follow-up questions

• What is the relationship between __eq__ and __hash__ in Python?

Sources

• Python documentation — Built-in functions: property