Assignment 3: Banking Returns

In this assignment, we will expand on the work we did on Week 1, and see how we can model different types of Bank Accounts using Inheritance.

Provided Code

Clone your repo using this link: https://github.com/kiboschool/programming2-w3-inheritance-acounts

main.py is where you will do the work. You will be expected to define three different subclasses there.

test.py is used for testing. You will not need to read it or modify it. Use python3 test.py to run the tests. At the beginning they should all fail.

If all tests pass by the time you submit you will earn full marks.

account.py contains a working implementation of the account class from Week 1. You are not expected to modify this file at all.

The Account class

As a quick refresher, let's go over the class:

• An Account object has two attributes: an owner which is a string, and a balance which is the amount of money stored in the account.
• we have an __str__() method, but it is not very helpful. You should ideally never see its output as you define the __str__() methods of our subclasses.
• we have a deposit() method which adds money to our balance.
• we have a withdraw() method which removes money from our balance if possible. This method returns True if the withdrawal was successful, and False otherwise.
• We have a transfer() method, which may be unfamiliar: This takes an amount and another account as a parameter - we call this account the recipient. We can then withdraw money from our account to deposit it in the recipient. This should only work if it's possible for us to withdraw the money in the first place. Make sure to study this method carefully, as you will need it later on.

Similarly to withdraw(), transfer() returns True if the transfer was successful and False otherwise.

Step 1: Checkings Account

Let's start with the simplest type of accounts, the checkings account. Create a subclass of Account called CheckingAccount and update it's __str__ method so that our output would look like this:

test_checking = CheckingAccount("Mehdi")
print(test_checking) # Display: Mehdi's Checking Account. Balance = 0

Convince yourself that CheckingAccount objects are able to handle the deposit, withdraw and transfer method.

Once you've convinced yourself that your code is correct. Run python3 test.py: You should pass 4/14 tests

Step 2: Customizing Savings Account

Savings accounts are interesting because they accrue interest. The bank will multiply your balance by a small factor called the interest rate, and add it to your account every month, or every year, depending.

Let's Create a savings account subclass of Account. It should have the following customizations:

• Its init method should also include an interest rate parameter, and it should have a new attribute for the interest rate.
• Its str method should clearly display that this is a savings account.
• It should have a new method, accrue_interest, which multiplies the balance by the interest value.

test_saving = SavingsAccount("Mehdi", 1) #1% interest rate

print(test_saving) # Display: Mehdi's Savings Account. Balance = 0

test_saving.deposit(200)
test_saving.accrue_interest() # Should increase our balance by 1%, in other words 2 

print(test_saving) # Display: Mehdi's Savings Account. Balance = 202

Convince yourself that SavingsAccount objects are able to handle the deposit, withdraw and transfer method.

Once you've convinced yourself that your code is correct. Run python3 test.py: You should pass 7/14 tests

Step 3: How do banks make money if they give you money?

If bans provide us interest, how do they make money? Well there are many strategies banks use, but one tricky one is that they charge users for making transfers.

Now Checking Accounts usually get free transfers, but Savings Accounts do not, since the bank spends money on them for interest. Let's replicate this in our code.

Modify the withdraw method for the SavingsAccount class only. If we try to withdraw money from the account, or transfer it to someone else, the account's balance should be reduced by an additional 5

test_saving = SavingsAccount("Mehdi", 1) #1% interest rate

print(test_saving) # Display: Mehdi's Savings Account. Balance = 0

test_saving.deposit(100)
test_saving.withdraw(10) # This should really remove 15

print(test_saving) # Display: Mehdi's Savings Account. Balance = 85 

test_saving.transfer(20, test_checking)# This should really remove 25 from test_saving

Once you've convinced yourself that your code is correct. Run python3 test.py: You should pass 9/14 tests

Step 4: LockedAccount

Another strategy banks use to make money is by holding your money for a long time. Some banks offer locked accounts: You can put money there, and it accrues interest like a savings account, but you are not allowed to take the money out for some amount of time.

Let's create a LockedAccount class. It should have the following customizations:

• Its init method should also include an interest rate parameter, and it should have a new attribute for the interest rate.
• Its str method should clearly display that this is a savings account.
• It should be able to accrue_interest, which multiplies the balance by the interest value.
• Calling withdraw() or transfer() on an account like this should always return False, and should not

Hint: What should the parent class of LockedAccount be? What saves you the most time?

test_locked = LockedAccount("Mehdi", 5) #5% interest rate

print(test_locked) # Display: Mehdi's Locked Account. Balance = 0

test_locked.deposit(100)

print(test_locked.withdraw(10)) # Display False
print(test_locked.transfer(20, test_checking))# Display False

test_locked.accrue(interest)

print(test_locked) # Display: Mehdi's Locked Account. Balance = 105 

Once you've convinced yourself that your code is correct. Run python3 test.py: You should pass 14/14 tests at this point!

Grading

Evidence of Persistence:

In the event that you are unable to get your program fully functional, you will receive partial credit based on your evidence showing the amount of effort that went into learning the underlying concepts to complete the assignment or that you persistently sought appropriate assistance. Examples of persistence may include, but is not limited to, the following: Git commit history showing evolution of your program, attendance to office hours (Instructor or TA), asking thoughtful questions in the appropriate Discord forums, formation of study groups, completion of additional practice exercises, reading of third-party resources, etc.

To receive partial credit, you must create a file called PERSISTENCE.md in your GitHub repo alongside the README.md file, and include your evidence of persistence, for example, links to your Discord questions, narrative explaining dates and times of office hour sessions that you attended and what you learned, links to resources that you referenced, links to ChatGPT conversations that you initiated (focusing on concepts not just getting answers), etc. The better you can demonstrate your work on learning, the easier it will be to provide partial credit, so be thorough. Make sure that file is properly committed to your repo, and included in your Gradescope submission.

Submitting Your Work

Your work must be submitted Anchor for degree credit and to Gradescope for grading.

For coding tasks involving Github Classroom:

1. Ensure that you commit and push your local code changes to your remote repository. (Note: In general, you should commit and push frequently, so that you have a backup of your work, so that there is evidence that you did your own work, and so that you can return to a previous state easily.)
2. Upload your submission to Gradescope via the appropriate submission link by selecting the correct GitHub repository from the drop-down list.
3. Export a zip archive of your GitHub repository by visiting your repo on GitHub, clicking on the green Code button, and selecting "Download Zip".
4. Upload the zip file of your repository to Anchor using the form below.

For cases where you answer questions on Gradescope:

1. Complete the work in Gradescope by navigating tot he appropriate link.
2. Export it as a pdf using th Google Chrome plugin: https://gofullpage.com/. This plugin will do multiple screen captures while scrolling through your document, and then stitch them into a pdf that you can download.
3. Upload the generated pdf to Anchor using the form below.

For any work completed outside of GitHub or Gradescope:

1. Take either screen captures of your work or export a pdf showing your complete work.
2. Submit the materials to Gradescope via the appropriate submission link for the course.
3. Upload the screen captures or pdf files to Anchor using the form below.

Note: Anchor submissions can occur at any time during the term, but it is critical that you upload all of your work to Anchor before the last day of the term. Gradescope submissions must be submitted before the deadline (or the late deadline, if applicable).