Inheritance.

You are asked to write software for a bank that represents two types of bank accounts - checking accounts and savings accounts. We'll discuss the differences between the two types of accounts and the methods/data they need to have. As both types of accounts share functionality, we will use inheritance to capture that common functionality.

• add(account) - add the given account instance (can be either a CheckingAccount or a SavingsAccount).

• pay_interest() - pay interest to all SavingsAccount instances. How to tell if a given account is a SavingsAccount? One way is to check the name of the class using account.__class__.__name__. Another is to simply check if the account instance has a pay_interest method using the hasattr function. See http://docs.python.org/library/functions.html#hasattr A third option is to put a call to an account's pay_interest method in a try: except: block and ignore the exception if it happens.

• pay_interest() - pay interest to all SavingsAccount instances. How to tell if a given account is a SavingsAccount? One way is to check the name of the class using account.__class__.__name__. Another is to simply check if the account instance has a pay_interest method using the hasattr function. See http://docs.python.org/library/functions.html#hasattr A third option is to put a call to an account's pay_interest method in a try: block and ignore the exception if it happens.

Lab 12

More object oriented programming

In lab 11 we created some classes to deal with bank accounts. In this lab we will create a class called Bank that stores bank accounts.

Your Bank class should support the following methods:

• add(account) - add the given account instance (can be either a CheckingAccount or a @@SavingsAccount).
• close(account_number) - close the account with the given number
• pay_interest() - pay interest to all SavingsAccount instances. How to tell if a given account is a SavingsAccount? One way is to check the name of the class using account.__class__.__name__. Another is to simply check if the account instance has a pay_interest method using the hasattr function. See http://docs.python.org/library/functions.html#hasattr

A third option is to put a call to an account's pay_interest method in a try: block and ignore the exception if it happens.

• total_balance() - returns the total balance in all the bank's accounts.
• __len__() - returns the number of accounts in the bank