Programming Assignment: Abstract Classes and Methods

Introduction

In this assignment, you will be creating an abstract class for a bank that will be used to create a regular class for a specific bank. This class will contain the implementation of the abstract method from the abstract class.

Instructions

1. Create a class called Bank and pass ABC to it.

2. Inside the class you have to define two methods:

2.1 Define a function called basicinfo() and add a print statement inside it saying "This is a generic bank" and returning the string "Generic bank: 0"
2.2 Define a second function called withdraw and keep it empty by adding a pass keyword under it. Make this function abstract by adding '@abstractmethod' right above it.

3. Create another class called Swiss and pass the class Bank inside it. This means you are inheriting from class Bank.

3.1 Create a constructor for this class that initializes a class variable bal to 1000

4. Override both functions from the Bank class: basicinfo() and withdraw().

4.1 Define a function called basicinfo() and add a print statement inside it stating “This is the Swiss Bank” and returning a string with "Swiss Bank: " followed by the current bank balance. For example, if self.bal = 80, then it would return "Swiss Bank: 80"

4.2 Define a second function, called withdraw and pass one parameter to it (other than self): amount. Amount represents the amount that will be withdrawn.
- 4.2.1 Update the class variable bal by deducting the value of amount from it.
- 4.2.2 Print the value of amount giving output such as: “Withdrawn amount: 30"
- 4.2.3 Print the new balance giving an output such as: “New balance: 970”
- 4.2.4 Return the new balance
- Note: Make sure to verify that there is enough money to withdraw! If amount is greater than balance, then do not deduct any money from the class variable bal, print a statement saying "Insufficient funds", and return the original account balance instead.

Solution

# Import ABC and abstractmethod from the module abc (which stands for abstract base classes)
from abc import ABC, abstractmethod

# Class Bank
class Bank(ABC):
    """ An abstract bank class

    [IMPLEMENT ME]
        1. This class must derive from class ABC
        2. Write a basicinfo() function that prints out "This is a generic bank" and
           returns the string "Generic bank: 0" 
        3. Define a second function called withdraw and keep it empty by
           adding the `pass` keyword under it. Make this function abstract by
           adding an '@abstractmethod' tag right above the function declaration.
    """
    @abstractmethod
    def withdraw(self, amount):
        pass

    def basicinfo(self):
        print("This is a generic bank")
        return "Generic bank: 0"

# Class Swiss
class Swiss(Bank):
    """ A specific type of bank than derives from class Bank

    [IMPLEMENT ME]
        1. This class must derive from class Bank
        2. Create a constructor for this class that initializes a class
           variable `bal` to 1000
        3. Implement the basicinfo() function so that it prints "This is the 
           Swiss Bank" and returns a string with "Swiss Bank: " (don't forget
           the space after the colon) followed by the current bank balance.

           For example, if self.bal = 80, then it would return "Swiss Bank: 80"

        4. Implement withdraw so that it takes one argument (in addition to
           self) that is an integer which represents the amount to be withdrawn
           from the bank. Deduct the withdrawn amount from the bank bal, print 
           the withdrawn amount ("Withdrawn amount: {amount}"), print the new
           balance ("New Balance: {self.bal}"), and return the new balance.

           Note: Make sure to verify that there is enough money to withdraw!  
                 If amount is greater than balance, then do not deduct any 
                 money from the class variable `bal`. Instead, print a 
                 statement saying `"Insufficient funds"`, and return the 
                 original account balance instead.
    """
    def __init__(self):
        self.bal = 1000

    def basicinfo(self):
        print("This is the Swiss Bank")
        return f"Swiss Bank: {self.bal}"

    def withdraw(self, amount):
        if amount > self.bal:
            print("Insufficient funds")
            return self.bal
        else:
            self.bal -= amount
            print(f"Withdrawn amount: {amount}")
            print(f"New balance: {self.bal}")
            return self.bal

# Driver Code
def main():
    assert issubclass(Bank, ABC), "Bank must derive from class ABC"
    s = Swiss()
    print(s.basicinfo())
    s.withdraw(30)
    s.withdraw(1000)

if __name__ == "__main__":
    main()

Programming Assignment: Abstract Classes and Methods - Module 3

Introduction

Instructions

Solution