Property Decorators (@property, @setter, @deleter)

1Concept

`@property` enables Pythonic getters and setters with validation logic without altering client API syntax (`obj.field` rather than `obj.get_field()`). It provides clean backward-compatible encapsulation.

2Architecture Diagram

Client access: acc.balance = 500 ---> Invokes @balance.setter ---> Validates (amount >= 0)

3Code Example

class BankAccount:
    def __init__(self, owner: str, initial_balance: float):
        self.owner = owner
        self._balance = initial_balance

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

    @balance.setter
    def balance(self, amount: float):
        if amount < 0:
            raise ValueError("Account balance cannot be negative!")
        self._balance = amount

acc = BankAccount("Alice", 1500.0)
acc.balance += 250.0
print(f"Updated balance for {acc.owner}: ${acc.balance:.2f}")

try:
    acc.balance = -50.0
except ValueError as e:
    print(f"Validation Blocked: {e}")

4Expected Output

Updated balance for Alice: $1750.00
Validation Blocked: Account balance cannot be negative!

5Key Takeaways

• ✓Properties allow adding validation logic without breaking existing code using attribute access.
• ✓Use leading underscore `_attr` to indicate private/internal attributes by convention.
• ✓Use `@property.deleter` to control resource cleanup when attributes are deleted via `del`.