Supermarket Self-Service Checkout

 Assignment 1 – Supermarket Self-Service Checkout

Assignment Overview

You are tasked with creating a text-based program for simulating a supermarket self-service checkout using the Python 3 programming language.

The assignment is broken up into four main components:

1.) Design and model two classes: Product and Checkout Register,

2.) Create an activity chart which describes the behaviour of the checkout system,

3.) Create a computer program that allows a user to interactively check out a number of products, then provides an opportunity to enter some virtual money to pay for the products and finally and prints out a receipt for the user (to the screen, not on paper), and finally

4.) Explain and integrate some code into your checkout program that places the products purchased into virtual shopping bags.

Your submission should consist of one Microsoft Word or LibreOffice document containing the first two parts of the assignment, and three Python scripts that implement the computer program (, and

The script runs the main logic of the program and will use instances of the Checkout Register and Product classes to simulate checking out of the supermarket.

You are provided with a Microsoft Word template to help you complete the first two parts of this assignment.

Towards the end of this document you will also be provided with the output of a simulated run of the completed computer program which may help you with this assignment.

Assignment Part 1 Details – Class Design

Think of a product that you can buy from a supermarket, like maybe a can of soup or an apple.

Start by listing all the properties of that object that you can think of – try to come up with at least ten general properties of a Product and write these down in your Assignment_Part_1_<YOUR_STUDENT_ID> Microsoft Word document.

Next, use the process of abstraction to cut the number of properties back to only four ‘key’ properties – write these down in the next section of your Word document. Take a look at the week 2 lecture slides if you need a reminder on how to go about this.

Now, fill in the class diagram for your Product class in the Word document template provided. Your product class does not have to have any methods (i.e. functions) associated with it to perform any actions other than a constructor which takes and set the four key properties that you’ve identified.

Next we’ll move on to CheckoutRegister class – think about what information the checkout has to keep track of to allow you to successfully check out of the supermarket. There will only really be three key properties that the CheckoutRegister cares about, and the CheckoutRegister class should have the following four methods available:

1)    A default constructor that takes no arguments and initialises a new object and its properties,
2)    accept_payment(some_amount),
3)    scan_item(some_product), and
4)    print_receipt().

Fill in the class diagram for the CheckoutRegister class in the Word template, and that’s the first part completed!

Assignment Part 2 Details – Activity Flowchart

Using either the online website (preferred), or the applications Visio or Powerpoint – create an activity diagram of how the program should operate to successfully scan one or more products, accept payment, provide change and print a receipt for the user.

Make sure to use the correct symbols in your diagram for starting, processes, decisions/branches, and ending the process.

Although you should be familiar with how a self-checkout works, if not then you can always go to a local supermarket with a self-checkout and buy a packet of chewing gum or something – or take a look at a YouTube video of self-service checkout, such as this one:

Don’t worry about loyalty/rewards cards to taking payment through debit or credit cards, our Checkout Register will only accept cash – although you can enter multiple denominations via multiple calls to the accept_money(some_amount) method. For example, calling accept_money(5.0) and then accept_ money(2.0) will mean that the Checkout Register knows that you have entered a total of $7.00. Also note that you can start the entire checkout process off by simply scanning a product.

Once you have completed your activity flowchart, add it to your assignment template document.

Assignment Part 3 Details – Software Implementation

You are free to implement the software however you see fit, however the functionality of the software should be able to match the following output. Note that in the below run of the program I have ‘hard-coded’ a small number of Product instances so that products exist which can they can be checked out – in your code you should do the same.

Your program does not have to have the facility to add new products – just define a few and use them as demonstrated below. If the final option of (N)ext customer is chosen, the program should run again

Example Program Output

----- Welcome to FedUni checkout! -----

Please enter the barcode of your item: 123
Milk, 2 Litres - $2.0

Would you like to scan another product? (Y/N) y

Please enter the barcode of your item: 456 Bread - $3.5

Would you like to scan another product? (Y/N) y

Please enter the barcode of your item: 999 This product does not exist in our inventory.

Would you like to scan another product? (Y/N) n

Payment due: $5.5. Please enter an amount to pay: 5

Payment due: $0.5. Please enter an amount to pay: -3
We don't accept negative money!
Payment due: $0.5. Please enter an amount to pay: 2

----- Final Receipt
Milk, 2 Litres
Total amount due:
Amount received:
Change given:

Thank you for shopping at FedUni!

(N)ext customer, or (Q)uit? q

Part 4 – Code Explanation and Use

You are provided with the following two functions which you should

1.     Analyse to determine what they do & provide documentation comments for, and

2.     Incorporate into your final program solution.

Wherever there is a # followed by some underscores in the code below, you should write a short comment explaining what the below section of code is doing, and if there is space why it is doing it. Do part 1 of the above in the provided assignment 1 template document, rather than here!

#   Function to: ___________________________

def get_float(prompt):

#   ____________________________________

value = float(0.0)

#   ____________________________________

while True: try:
#   ____________________________________

value = float(input(prompt))

#   ____________________________________

if value < 0.0:

print("We don't accept negative money!") continue

#   ____________________________________


#   ____________________________________

except ValueError:
print('Please enter a valid floating point value.')

#   ____________________________________

return value

#   Function to: ___________________________

def bag_products(product_list):

#   ____________________________________

bag_list = []

non_bagged_items = [] MAX_BAG_WEIGHT = 5.0

#   ____________________________________

for product in product_list:

#   ____________________________________

if product.weight > MAX_BAG_WEIGHT: product_list.remove(product) non_bagged_items.append(product)

#   ____________________________________

current_bag_contents = [] current_bag_weight = 0.0

#   ____________________________________

while len(product_list) > 0:

#   ____________________________________

temp_product = product_list[0] product_list.remove(temp_product)

#   ____________________________________

if current_bag_weight + temp_product.weight <= MAX_BAG_WEIGHT:

#   ____________________________________

current_bag_contents.append(temp_product) current_bag_weight += temp_product.weight

#   ____________________________________



#   ____________________________________

current_bag_contents = [temp_product] current_bag_weight = temp_product.weight

#   ____________________________________

if (len(product_list) == 0):


#   ____________________________________

for index, bag in enumerate(bag_list):

output = 'Bag ' + str(index + 1) + ' contains: '

#   ____________________________________

for product in bag:

output += + '\t' print(output, '\n')

#   ____________________________________

if (len(non_bagged_items) > 0):
output = 'Non-bagged items: '

#   ____________________________________

for item in non_bagged_items:

output += item + '\t' print(output,'\n')

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