09 Prove Milestone: Text Files

Purpose

Prove that you can write a Python program that reads CSV files and creates, populates, and uses a dictionary.

Problem Statement

A local grocery store subscribes to an online service that enables its customers to order groceries online. After a customer completes an order, the online service sends a CSV file that contains the customer’s requests to the grocery store. The store needs you to write a program that reads the CSV file and prints a receipt in the terminal window that lists the purchased items and shows the subtotal, the sales tax amount, and the total.

Assignment

During this milestone, you will write half of a Python program named receipt.py that prints a receipt in the terminal window for a customer’s grocery order. Specifically, by the end of this milestone, your program must read and process these two CSV files:

• The products.csv file is a catalog of all the products that the grocery store sells.
• The request.csv file contains the items ordered by a customer.

Help

If you’re having trouble completing this assignment, reading related online documentation, using a generative AI as a tutor, or working with a human tutor will help you complete it.

Steps

Do the following:

1. Download both of these files: products.csv and request.csv and save them in the same folder where you will save your Python program.
2. Open the products.csv file in VS Code and examine it. Notice that each row in this file contains three values separated by commas: a product number, a product name, and a retail price. Also, notice that each product number in the products.csv file is unique. This means that your program can read the products.csv file into a dictionary and use the product numbers as dictionary keys.
3. In VS Code, create a new file and save it as receipt.py in the same folder where you saved the products.csv and request.csv files.
4. In receipt.py, write code to open the products.csv file and read its rows into a compound dictionary. Because you want to write a well-organized program, does it seem like a good idea to put this code into a function? Will this function need any parameters? As part of the team activity for this lesson, you already wrote a similar function.
5. Open the request.csv file in VS Code and examine it. Notice that each row contains only two values, a product number and a quantity. Notice also that product number D083 appears twice in the file because the customer who created the order in the request.csv file added four yogurts to his order and then later added three more yogurts to his order. Because product numbers may appear multiple times in the request.csv file, your program should not read the contents of request.csv into a dictionary.

6. In your receipt.py program, write code to open the request.csv file and read and process each row. Because you want to write a well-organized program, does it seem like a good idea to put this code into a function? Will this function need any parameters? Your code that reads the request.csv file must do the following:

   1. Open the request.csv file for reading.
   2. Skip the first line of the request.csv file because the first line contains column headings.
   3. Use a loop that reads and processes each row from the request.csv file. Within the body of the loop, your program must do the following for each row:

      1. Use the requested product number to find the corresponding item in the products_dict.
      2. Print the product name, requested quantity, and product price.
7. In your receipt.py program, write another function named main that does the following:

   1. Calls your function that reads from the products.csv file into a compound dictionary and stores the returned compound dictionary in a variable named products_dict. Does your function have any parameters? If so, did you add arguments to the function call?
   2. Prints the products_dict.
   3. Calls your function that reads and processes the request.csv file. Does your function have any parameters? If so, did you add arguments to the function call?
8. At the bottom of your receipt.py file, add a call to the main function. Be certain to protect the call to main with an if statement as taught in the preparation content for lesson 5.

Testing Procedure

Verify that your program works correctly by following each step in this testing procedure:

1. Run your program and verify that it prints the products dictionary and requested items as shown in the sample output below.

   > python receipt.py
   
   All Products
   {'D150': ['D150', '1 gallon milk', '2.85'], 'D083': ['D083',
   '1 cup yogurt', '0.75'], 'D215': ['D215', '1 lb cheddar
   cheese', '3.35'], 'P019': ['P019', 'iceberg lettuce',
   '1.15'], 'P020': ['P020', 'green leaf lettuce', '1.79'],
   'P021': ['P021', 'butterhead lettuce', '1.83'], 'P025':
   ['P025', '8 oz arugula', '2.19'], 'P143': ['P143', '1 lb
   baby carrots', '1.39'], 'W231': ['W231', '32 oz granola',
   '3.21'], 'W112': ['W112', 'wheat bread', '2.55'], 'C013':
   ['C013', 'twix candy bar', '0.85'], 'H001': ['H001', '8
   rolls toilet tissue', '6.45'], 'H014': ['H014', 'facial
   tissue', '2.49'], 'H020': ['H020', 'aluminum foil', '2.39'],
   'H021': ['H021', '12 oz dish soap', '3.19'], 'H025':
   ['H025', 'toilet cleaner', '4.50']}
   
   Requested Items
   wheat bread: 2 @ 2.55
   1 cup yogurt: 4 @ 0.75
   32 oz granola: 1 @ 3.21
   twix candy bar: 2 @ 0.85
   1 cup yogurt: 3 @ 0.75

Common Mistake

Counting Only Three D083 Yogurts

Because product number D083 appears twice in the request.csv file, your program should not read the request.csv file into a dictionary. Recall that each key in a dictionary is unique. If your program reads the request.csv file into a dictionary, when your program reads line 3 of the request.csv file, your program will store a request for four yogurts into the dictionary. Then when it reads line 6 of the request.csv file, your program will replace the request for four yogurts with a request for three yogurts. In other words, if your program reads the request.csv file into a dictionary, your program will think that the customer ordered only three yogurts instead of the seven (4 + 3) that he ordered. Therefore, your program should not read the request.csv file into a dictionary but should instead read and process each row similar to example 3 in the preparation content for this lesson.

Submission

On or before the due date, return to I‑Learn and report your progress on this milestone.