Encapsulation

Encapsulation

Encapsulation hides internal data and only exposes what's necessary. In Python, prefix an attribute with __ to make it private.

Private Attributes

class BankAccount:
    def __init__(self, owner, balance):
        self.owner = owner
        self.__balance = balance

    def deposit(self, amount):
        self.__balance += amount

    def get_balance(self):
        return self.__balance

acc = BankAccount("Alice", 1000)
acc.deposit(500)
print(acc.get_balance())
# print(acc.__balance)  # AttributeError

Property Decorators

Use @property for getters and @setter for controlled attribute access.

class Temperature:
    def __init__(self, celsius):
        self._celsius = celsius

    @property
    def celsius(self):
        return self._celsius

    @celsius.setter
    def celsius(self, value):
        if value < -273.15:
            raise ValueError("Too cold!")
        self._celsius = value

    @property
    def fahrenheit(self):
        return self._celsius * 9 / 5 + 32

t = Temperature(25)
print(t.celsius)
print(t.fahrenheit)
t.celsius = 30
print(t.fahrenheit)