EX02 - Basic Functions

In Exercise 02 you will translate your programs from Exercise 01 into well structured programs made of functions.

Due to the wellness weekend, we are breaking this exercise into two parts. (Each will be considered its own free-standing smaller exercise for final grade tabulation purposes.)

Part 1 is made of two programs and due Friday, 2/12 at 11:59pm (5% early EC by Wednesday, 3% EC by Thursday):

  1. A good vibes fortune cookie
  2. A little logical puzzle

Part 2 is a single program and due Thursday, 2/18 at 11:59pm (5% early EC by Tuesday 2/16, 3% EC by Wednesday 2/17):

  1. A vaccine calculator

0. Pull the skeleton code

You will find the starter files needed by “pulling” from the course workspace repository. Before beginning, be sure to:

  1. Be sure you are in your course workspace. Open the file explorer and you should see your work for the course. If you do not, open your course workspace through File > Open Recent.
  2. Open the Source Control View by clicking the 3-node (circles) graph (connected by lines) icon in your sidebar or opening the command palatte and searching for Source Control.
  3. Click the Ellipses in the Source Control pane and select “Pull, Push” from the drop-down menu, then select “Pull from…” A box will appear and you should select either “origin” or “upstream”, but not “backup”. This will begin the pulling process from the course repository. It should silently succeed. (If you are on macOS and do not see anything in source control anymore, it may be because of a macOS update. You can typically resolve this by opening a new Terminal, typing the command xcode-select --install, pressing enter and following its instructions.)
  4. Return to the File Explorer pane and open the exercises directory. You should see it now contains two other directores named ex02_p1 and ex02_p2. If you expand those directories, you will see the starter files for the three Python programs in this exercise.

After pulling the skeleton code, above, you can find the starter code for all the functions in the file exercises/ex02_p1/fortune_cookie.py.

We have provided the skeleton of a main function, discussed in lecture on Tuesday 2/9, and have denoted 2x TODO comments for you to complete in order.

First, find TODO 1 and notice it is at the “top-level” of the file (no indentation). Your job here is to define a function named fortune_cookie. It has the following signature expectations:

  1. It should have zero parameters.
  2. It should return a str value.

The str it returns should be a single, random fortune string. You can reuse your logic from ex01, but you will need to be careful with two particular changes:

  1. The logic be indented such that it is a part of the fortune_cookie function’s body block.
  2. You will need to return the generated str value. Do not print the fortune from within the function!

Second, find TODO 2 inside of the main function’s body. Replace this comment with a statement that prints the result of calling the fortune_cookie function you defined below. Hint: function calls must always have a pair of parentheses () following the name of the function, even if there are no arguments to pass.

You should now be able to run your program:

python -m exercises.ex02_p1.fortune_cookie

Requirements

  • This function should return just the one-line fortune. This is the second line of output from ex01. The fortune_cookie function must not have any calls to print inside of it.
  • Only make one call to randint and store the result in a variable
  • Use nested if/else conditional statements within else blocks to control which fortune is returned. In other words, do not use four linear, unrelated if statements.

Program 2. Tar Heel Arithmetic

The next program involves the same small logical and arithmetic puzzle from part 2 of ex01. You will notice the user is asked for an int in exercises/ex02_p1/tar_heels.py and their response is stored in the variable choice within the main function’s frame.

First, find TODO 1 and define a function named tar_heels. Its signature has the following additional expectations:

  1. A single parameter of type int. You can decide an appropriate name for it!
  2. It should return a str value.

The body of the tar_heels function should meet the following criteria, which you implemented in the previous exercise:

  • When response is divisible by 2, return “TAR”.
  • When response is evenly divisible by 7, return “HEELS”.
  • When response is evenly divisible by both 2 and 7, return “TAR HEELS” instead of just “TAR” or “HEELS”
  • When none of the above conditions are met, return “CAROLINA”

Second, after defining the tar_heels function, find TODO 2 in the main function. Replace this comment with a statement that prints the value returned by calling tar_heels and giving the user’s choice as an argument to the function call.

Once your function definition and function call are in place at their respective TODOs, you should be able to run your program:

python -m exercises.ex02_p1.tar_heels

Part 2. Vaccine Calculator

The second part of this exercise is to rewrite the vaccine_calc.py program as a well-structured program made of functions.

Unlike the programs of Part 1, your original vaccine_calc program will be subdivided into a main function, which gathers user inputs, and two functions representing parts of the overall computation:

  1. The days_to_target function will take the user inputs and return an int number of days until reaching the target with the same logic as ex01.
  2. The future_date function will take an int number of days and return a str representation of the date that is int number of days from now.

Let’s break down each of these steps, including the specific requirements:

Part 2.1

The first natural step of our program from ex01 was to calculate the number of days needed to get the targeted percentage of the population vaccinated.

At TODO 1, define a function named days_to_target. Its signature is expected to meet the following requirements:

  1. Four parameters, each of type int, corresponding to the following inputs in this exact order:
    1. population
    2. doses
    3. doses_per_day
    4. target (out of 100)
  2. The function is expected to return an int value.

The function should compute and return the number of days until the target percentage is vaccinated based on the 4 int parameters. Your model should make the same assumptions from ex01.

Once you have implemented your function, at TODO 2 in the main function, declare a variable to store the result of calling the function you just defined with the user’s inputs.

To test whether you are on the right track, you can add a “debugging print” statement just after the variable declaration to print its contents. A “debugging print” statement is just an ordinary print statement that’s used while you’re working on a project to confirm you are on the right track. It’s like checking over your work and confirming your assumptions. You’ll remove it once you have convinced yourself your function definition and call are correct.

Part 2.2

The second step of this program is getting the projected date that this vaccination goal will be reached. Given an int representing the number of days to go, your function will return a string in the form of Month DD, YYYY.

First, at TODO 3, define a function named future_date. Its signature line will have the following expectations:

  1. Takes in a parameter of type int representing the number of days out in the future. Name this parameter anything you’d like.
  2. Returns a string value.

In the body of the function, you will reproduce the steps you took in the previous exercise to go from an int number of days to a str representing a future date. You will once again make use of the datetime and timedelta concepts. Your code will likely be very similar, if not the same, except that perhaps the variable name of your “days” parameter will be different and you will need to return the formatted date string. Once again, the format string is expected to use the following format: ""%B %d, %Y""

Second, at TODO 4, declare a variable that is assigned the result of calling future_date and giving it the number of days you calculated in the variable above as an argument to the call.

Finally, at TODO 5, print the expected output by concatenating a string and using the variables you established above. The expected output will look something like the following, with the specific components of % vaccination, days, and specific date replaced based on the program’s calculations:

We will reach 50% vaccination in 25 days, which falls on February 28, 2021.

3. Make a Backup Checkpoint “Commit”

As you make progress on this exercise, making backups is encouraged. Note that you do not have to make a backup in order to submit your work, though you are encouraged to before each submission so that you can revert back to a previous point in your project if you accidentally change something you did not intend to.

  1. Open the Source Control panel (Command Palette: “Show SCM” or click the icon with three circles and lines on the activity panel).
  2. Notice the files listed under Changes. These are files you’ve made modifications to since your last backup.
  3. Move your mouse’s cursor over the word Changes and notice the + symbol that appears. Click that plus symbol to add all changes to the next backup. You will now see the files listed under “Staged Changes”.
    • If you do not want to backup all changed files, you can select them individually. For this course you’re encouraged to back everything up.
  4. In the Message box, give a brief description of what you’ve changed and are backing up. This will help you find a specific backup (called a “commit”) if needed. In this case a message such as, “Progress on Exercise 2” will suffice.
  5. Press the Check icon to make a Commit (a version) of your work.
  6. Finally, press the Ellipses icon (…), look for “Pull/Push” submenu, and select “Push to…”, and in the dropdown select your backup repository.

4. Submit to Gradescope for Grading

Login to Gradescope. There will be two assignments for this exercise based on the separate parts with separate deadlines. For each, you’ll see an area to upload a zip file. To produce a zip file for autograding, return back to Visual Studio Code.

If you do not see a Terminal at the bottom of your screen, open the Command Palette and search for “View: Toggle Integrated Terminal”.

To produce a zip file for ex02_p1, type the following command (all on a single line):

python -m tools.submission exercises/ex02_p1

To produce a zip file for ex02_p2, type the following command (all on a single line):

python -m tools.submission exercises/ex02_p2

In the file explorer pane, look to find the zip file named “21.mm.dd-hh.mm-exercises-ex02_p1.zip” (or p2). The “mm”, “dd”, and so on, are timestamps with the current month, day, hour, minute. If you right click on this file and select “Reveal in File Explorer” on Windows or “Reveal in Finder” on Mac, the zip file’s location on your computer will open. Upload this file to Gradescope to submit your work for this exercise.

Autograding will take a few moments to complete. If there are issues reported, you are encouraged to try and resolve them and resubmit. If for any reason you aren’t receiving full credit and aren’t sure what to try next, come give us a visit in office hours!