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We have been learning about Object Orientated Programming in my Computer Science lessons but the code that we were given as an example doesn't seem to work properly.

class bankAccount(): 

    '''This is a bank account class'''

    def __init__(self, account_name = "Bank Account", balance = 1500):
        self.__account_name = account_name 
        self.__balance = balance 

    def deposit(self, value): 
        self.__balance = self.__balance + value 
        print("You now have: ", self.__balance) 

    def withdraw(self, value): 
        self.__balance = self.__balance - value 
        print("You now have: ", self.__balance) 

class currentAccount(bankAccount): 

    '''This is a current account class''' 

    def __init__(self, account_name = "Current Account", balance = 1500): 
        self.__account_name = account_name 
        self.__balance = balance

        super().__init__() 

    def withdraw(self, value): 

        if value > 1000: 
            print("You will have to phone the bank manager") 

        else: 
            self.__balance = self.__balance - value 
            print("You now have: ", self.__balance) 

class savingsAccount(bankAccount): 

    '''This is a current account class''' 

    def __init__(self, account_name = "Savings Account", balance = 1500): 
        self.__account_name = account_name 
        self.__balance = balance 

        super().__init__() 

    def deposit(self, value): 
        self.__balance = self.__balance + (value *1.03) 
        print("You now have: ", self.__balance) 

currentObject = currentAccount() 

savingsObject = savingsAccount() 

while True: 
    print("1. Current Account") 
    print("2. Savings Account")

    menu_option = int(input()) 

    if menu_option == 1: 
        print("1. Deposit funds") 
        print("2. Withdraw funds") 

        submenu_option = int(input()) 

        if submenu_option == 1: 
            value = int(input("How much would you like to deposit? ")) 
            currentObject.deposit(value) 

        elif submenu_option == 2: 
            value = int(input("How much would you like to withdraw? ")) 
            currentObject.withdraw(value) 
        else: 
            print("Wrong menu choice!") 

    elif menu_option == 2: 
        print("1. Deposit funds") 
        print("2. Withdraw funds")

        submenu_option = int(input()) 

        if submenu_option == 1: 
            value = int(input("How much would you like to deposit? ")) 
            savingsObject.deposit(value) 

        elif submenu_option == 2: 
            value = int(input("How much would you like to withdraw? ")) 
            savingsObject.withdraw(value) 

        else: 
            print("Wrong menu choice!") 

    else: 
        print("Wrong menu choice!") 

input()

Seemingly there is a separate data stored for each withdrawal and deposit. For example, if you deposit 100 from a savings account and then withdraw 100, instead of going from (1500 + 100) = 1600 and then doing (1600 - 100) the program seems to default back to using 1500 as the initial balance creating different balances for when you deposit and withdraw.

Any help would be greatly appreciated as OOP is new to me, and I can't figure out why this is happening.

T Burnard
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1 Answers1

0

The reason for the confusion is that you use the self.__balance. The double underscore in the attribute names is a special case that activates a Name Mangling: What is the meaning of a single and a double underscore before an object name?

To fix your problem just switch all your class attributes names to a single underscore prefix:

class bankAccount(): 

    '''This is a bank account class'''

    def __init__(self, account_name = "Bank Account", balance = 1500):
        self._account_name = account_name 
        self._balance = balance 

    def deposit(self, value): 
        self._balance = self._balance + value 
        print("You now have: ", self._balance) 

    def withdraw(self, value): 
        self._balance = self._balance - value 
        print("You now have: ", self._balance) 

class currentAccount(bankAccount): 

    '''This is a current account class''' 

    def __init__(self, account_name = "Current Account", balance = 1500): 
        self._account_name = account_name 
        self._balance = balance

        super().__init__() 

    def withdraw(self, value): 

        if value > 1000: 
            print("You will have to phone the bank manager") 

        else: 
            self._balance = self._balance - value 
            print("You now have: ", self._balance) 

class savingsAccount(bankAccount): 

    '''This is a current account class''' 

    def __init__(self, account_name = "Savings Account", balance = 1500): 
        self._account_name = account_name 
        self._balance = balance 

        super().__init__() 

    def deposit(self, value): 
        self._balance = self._balance + (value *1.03) 
        print("You now have: ", self._balance) 

currentObject = currentAccount() 

savingsObject = savingsAccount() 

while True: 
    print("1. Current Account") 
    print("2. Savings Account")

    menu_option = int(input()) 

    if menu_option == 1: 
        print("1. Deposit funds") 
        print("2. Withdraw funds") 

        submenu_option = int(input()) 

        if submenu_option == 1: 
            value = int(input("How much would you like to deposit? ")) 
            currentObject.deposit(value) 

        elif submenu_option == 2: 
            value = int(input("How much would you like to withdraw? ")) 
            currentObject.withdraw(value) 
        else: 
            print("Wrong menu choice!") 

    elif menu_option == 2: 
        print("1. Deposit funds") 
        print("2. Withdraw funds")

        submenu_option = int(input()) 

        if submenu_option == 1: 
            value = int(input("How much would you like to deposit? ")) 
            savingsObject.deposit(value) 

        elif submenu_option == 2: 
            value = int(input("How much would you like to withdraw? ")) 
            savingsObject.withdraw(value) 

        else: 
            print("Wrong menu choice!") 

    else: 
        print("Wrong menu choice!") 

input()
ababak
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