Encapsulation Mastery

class BankAccount: """ Encapsulation Example: Private attributes with controlled access """ def __init__(self, account_number, initial_balance=0): # Private attributes (name mangling with __) self.__account_number = account_number self.__balance = initial_balance self.__transactions = [] # Getter methods (controlled read access) def get_balance(self): """Public method to access private balance""" return self.__balance def get_account_number(self): """Public method to access private account number""" return self.__account_number # Controlled modification with validation def deposit(self, amount): """Public method to modify balance with validation""" if amount <= 0: raise ValueError("Deposit amount must be positive") self.__balance += amount self.__add_transaction("Deposit", amount) return True def withdraw(self, amount): """Public method with business logic validation""" if amount <= 0: raise ValueError("Withdrawal amount must be positive") if amount > self.__balance: raise ValueError("Insufficient funds") self.__balance -= amount self.__add_transaction("Withdrawal", -amount) return True # Private helper method (internal implementation) def __add_transaction(self, transaction_type, amount): """Private method - hidden from outside access""" transaction = { 'type': transaction_type, 'amount': amount, 'balance_after': self.__balance } self.__transactions.append(transaction) def get_transaction_history(self): """Controlled access to transaction history""" return self.__transactions.copy() # Usage Example account = BankAccount("12345", 1000) # ✅ Correct usage - through public interface print(f"Balance: ${account.get_balance()}") account.deposit(500) account.withdraw(200) # ❌ This would fail - direct access to private attributes # print(account.__balance) # AttributeError # ✅ Controlled access works print(f"Final balance: ${account.get_balance()}")