COMPS III: Unit 3 Code Along

Overview

Object oriented programming is something that is utilized by nearly every business. To illustrate its utility, we will be building an e-commerce application together using object oriented programming over the next three units.

This week, we’ll be implementing a Product class to represent the products in our store and a ShoppingCart class to store the Product(s) the user has selected.

VS Code - app.py has syntax instructions

1. Define a Product class.
2. Define constructor with names (String), price (float), and sku (int).
3. Assign params to properties.
4. In the tests folder there is a test called test_can_create_product that tests that you can...create a product. You can set these up to run in your VS Code by doing the following:
   • Press the "Testing" flask icon in the left hand toolbar.
   • Press "Configure Python Tests"
   • Select "pytest"
   • Select the "root directory"
   • You can now run some or all of the tests in the left hand menu.

VS Code - main.py has syntax instructions

5. Import the Product class into the file.
6. Create main() function that will hold all of our program runs. Call the function.
7. Create two instances of the Product class and print out the attributes. To see the output run python3 main.py in the command line.
8. Print out the object. You should see something like <app.Product object at 0x1007e2e40>. This is listing the memory address on our computer for the Product object, but that's not particularly useful. We can create a __str__() method to print out something more useful.

VS Code - app.py has syntax instructions

9. Create a __str__() method that takes the object as an argument and returns a string printing out the information about the object. This string should be in the format "[NAME] (SKU: [SKU]) - $[PRICE]".
10. The test_product_str test should now be passing.

Local Terminal - bash.sh has syntax instructions

11. Verify that the properties print out as expected using the command python3 main.py.

VS Code - app.py has syntax information

12. Create a ShoppingCart class.
13. Define constructor with items (list) that will hold a list of Product objects.
14. Define a __str()__ method that prints out information about the ShoppingCart object. This string should be in the format "Shopping Cart with [NUMBER_OF_ITEMS] items."".
15. The test_can_create_shoppingcart and test_shoppingcart_str tests should now be passing.

VS Code - main.py has syntax information

16. Import the ShoppingCart class into the file.
17. Inside main(), create an instance of the shopping cart and print it to the console.

VS Code - app.py has syntax information

18. Define a add_items method that takes the object, a product, and a quantity as an argument and does the following: - If no quantity is provided, it should be set to 1. - Add the item to the object's items list. It should be added as a dictionary in the format {"product": [PRODUCT_OBJECT], "quantity": [QUANTITY]}.
19. Define a get_total method that takes the object as an argument and does the following:
    • Initialize a variable called total with a value of zero.
    • Iterate through items and total up the cost of all the items in the cart
    • Return total
20. Define a display_cart method that takes the object as an argument and does the following:
    • Iterate through the items in the cart and print out a string in the format "[PRODUCT_NAME] - Quantity: [QUANTITY]')"
    • When the iteration is complete, print the total cost of all the items in the format "Total: $[TOTAL]".
21. The test_shoppingcart_add_items should now be passing.

VS Code - main.py has syntax information

22. Add each of the Product objects you created in step 9 to the ShoppingCart instance using the add_items method.
23. Display the cart contents using the display_cart method.
24. Call get_total to see the total cost of everything that you added to the cart.