How do you call a child class pythonically?

Question

I have recently begun learning OOP with Python, and to test my class building and inheritance skills I have built a simple framework for a banking application. As far as I can see, based on my knowledge of how inheritance is performed in OOP, there is nothing wrong with my code syntax-wise:

import pickle, sys, datetime

class Bank():

    def __init__(self):
        with open('accounts.txt','rb') as fp:
            accounts=pickle.load(fp)

    def exit(self):
        with open('accounts.txt','wb') as fp:
            pickle.dump(accounts,fp)
        sys.exit()

class TransactionMenu(Bank):

    def __str__(self,account):
        if str(super().accounts[account])[::-1].find('.')==-1:
            nT=str(super().accounts[account])+'.00'
        elif str(super().accounts[account])[::-1].find('.')==1:
            nT=str(super().accounts[account])+'0'
        else:
            nT=str(super().accounts[account])
        return '£'+nT

    def balanceEnquiry(self,account):
        print('Date:    '+datetime.datetime.now()+'\n'+'Account name:    '+account+'\n'+'Balance:    '+self.__str__(account))

    def deposit(self,account):
        while True:
            print('current balance:    '+self.__str__(account))
            amt=input('enter deposit amount: ')
            try:
                if '.' in amt:
                    amt=float(amt)
                else:
                    amt=int(amt)
                super().accounts[account]+=amt
                print('new balance:    '+self.__str__(account))
                break
            except:
                pass

    def withdraw(self,account):
        while True:
            print('current balance:    '+self.__str__(account))
            amt=input('enter withdrawal amount: ')
            try:
                if '.' in amt:
                    amt=float(amt)
                else:
                    amt=int(amt)
                super().accounts[account]-=amt
                print('new balance:    '+self.__str__(account))
                break
            except:
                pass

    def __init__(self,account):    
        while True:
            choice=input('enter balance enquiry, deposit, withdraw or exit: ').lower()
            if choice=='b' or choice=='balance' or choice=='balance enquiry' or choice=='enquiry' or choice=='balance enquiry' or choice=='bal':
                self.balanceEnquiry(account)
            elif choice=='d' or choice=='deposit':
                self.deposit(account)
            elif choice=='w' or choice=='withdraw':
                self.withdraw(account)
            elif acc=='e' or acc=='exit':
                super().exit()

class Menu(Bank):

    def logIn(self):
        while True:
            accN=input('enter your account name or exit: ').lower()
            if acc=='e' or acc=='exit':
                super().exit()
            else:
                for account in super().accounts:
                    if accN==account:
                        TransactionMenu(accN)
                        break

    def createAccount(self):
        while True:
            newAcc=input('enter your forename and surname or exit: ').lower()
            if acc=='e' or acc=='exit':
                super().exit()
            else:
                super().accounts[newAcc]=0.00

    def __init__(self):
        while True:
            acc=input('enter login, register or exit: ').lower()
            if acc=='l' or acc=='login' or acc=='log in' or acc=='log-in':
                self.logIn()
                break
            elif acc=='r' or acc=='register' or acc=='reg':
                self.createAccount()
                break
            elif acc=='e' or acc=='exit':
                super().exit()


Bank().Menu()

However, when I call Bank().Menu(), I get the following error:

Traceback (most recent call last):
  File "C:\Users\xavier\Desktop\bank\bank.py", line 104, in <module>
    Bank().Menu()
AttributeError: 'Bank' object has no attribute 'Menu'

This would imply that I have not performed my inheritance properly, however I can't see how this is the case.

Any help is much appreciated.

Answer 1

By defining Menu like class Menu(Bank) means that Bank is the superclass of Menu .

Menu will inherit everything from Bank but that inheritance can be overidden by redefining in the child class.

Declaring something as a superclass does not define the child class inside of the superclass as far as I know.

I'm not sure what you are trying to do, so it's hard to give you a suggestion of what you should do. I hope this explains something though.