Week 7 — Functions That Hand Back Their Work

Assignment 7 of the term — predict what a function hands back, see why argument order matters, tell print from return, and explain it all to someone who has never programmed.

This adaptive assignment uses a coaching dialogue to help you turn a first attempt into a clear, evidence-based report. You remain the author. The coach asks questions, checks the reasoning you show, and waits for you to revise before it produces the required report. This builds on Weeks 5 and 6: a function packages the expressions and loops you already write into one named piece of work. This week's lecture tutorial, quiz, discussion, and Coding Lab practise the same ideas from other angles; this assignment is where you put them together, and it is the last assignment before next week's midterm review.

The task

A neighbor who runs a community garden wrote a short program to count the plots still free and add 5 new ones the garden is building:

def plots_left(total, rented):
    print(total - rented)

left = plots_left(40, 25)
print(left + 5)

It printed 15 and then stopped with an error. Your neighbor says, "Python lost my number." Your job is to check what Python really did, the way a programmer would: predict each output before you run it, run it in a free browser Python runner, and explain what happened. All four problems are illustrative; Problems 1 and 2 use this week's reading log, whose goal is 300 pages with 45 pages read at the start.

Work these four problems. For each one, write your prediction first, then run the code and write the actual output beside your prediction:

1. The reading log's function def pages_left(goal, pages_read): returns goal - pages_read and is called as print(pages_left(300, 45)). What does the program print?
2. The same function is called as print(pages_left(45, 300)), with the arguments in the other order. What does the program print?
3. Your neighbor's function is fixed to return total - rented; the program runs left = plots_left(40, 25) and then print(left + 5). What does it print?
4. The temperature converter def to_fahrenheit(celsius): returns celsius * 9 / 5 + 32 and is called as print(to_fahrenheit(20)). What does the program print?

Beside each answer, add one brief interpretation:

• Problem 1: state which value goal and which value pages_read hold during the call, and name the two local names that vanish when the call ends.
• Problem 2: explain why swapping the arguments changes the printed value, and name the kind of error this slip is.
• Problem 3: run your neighbor's original printing version, report what it prints and the exception type on the last line of its error, and explain why changing print to return fixes it.
• Problem 4: explain why the printed value ends in .0, then store the returned value with reading = to_fahrenheit(20), run print(reading), and report what prints.

Explain it to a non-programmer

Write a 3–5 sentence message to your neighbor that explains, in everyday words, why Python seemed to lose the number and how changing one word in the function fixes it. Use the idea that showing a value on the output is different from handing it back to the rest of the program, and name one limit or caveat, such as what the program must now do to display the count. Explain any technical term in everyday words. More than one good message is possible.

For a different, ungraded example, imagine a roommate whose bill-splitting function takes the bill first and the number of people second, but who called it with the number of people first. Model message: "Your function fills its two slots in order: the first value you give it goes into the bill slot, and the second goes into the people slot. You handed it the people count first, so it treated the number of people as the bill and the bill as the number of people. Python did exactly what the order said, which is why there was no error message, only a strange amount. One catch: Python cannot warn you about this kind of mix-up, so read the first line of the function before you call it."

Use that pattern for your neighbor's question, with your own wording and evidence.

Part 1 — Student instructions

1. Draft all four predictions, the four actual outputs, the four brief interpretations, and your message to your neighbor before opening a chatbot. Run every program yourself in a browser Python runner.
2. Open any course-approved chatbot. Copy the entire Coach Prompt box, including its first and last marker lines, and paste it as one message. The coach will ask for your draft and then work one question at a time.
3. Answer in your own words. Show your traces when asked. Use the coach's feedback to revise at least one trace or explanation, even if your first attempt was correct.
4. Continue until the prompt's exit condition is met.
5. Save the chat's share link and copy the final report exactly as the coach gives it.

The chatbot is a coach, not a ghostwriter. It must draw out your reasoning rather than write the work for you, and it does not run your code; your own runs settle every output.

Coach Prompt

COPY EVERYTHING BELOW THIS LINE
ROLE: You are a careful learning coach for an introductory computer science course taught in Python 3. Draw out and challenge MY thinking about functions, parameters and arguments, return and print, and local and global names. Do not write my assignment for me, do not invent work I did not show, never invent a statistic, a study, or a quotation, and never tell me what a line of code prints: ask me to run it in my own browser Python runner and tell you what appeared.

ASSIGNMENT: Work through these four problems in order, one at a time. Do not invent, replace, or reorder a problem. All four are illustrative. For each one I write a prediction first, then run the code and report the actual output beside it.
PROBLEM P1: The reading log's function returns goal minus pages read and is called with the arguments 300 and 45, in that order, inside print. What does the program print?
PROBLEM P2: The same reading-log function is called with the arguments 45 and 300, in that order, inside print. What does the program print?
PROBLEM P3: The garden function is fixed to return total minus rented; the program stores the call with the arguments 40 and 25 in a name and prints that name plus 5. What does it print?
PROBLEM P4: The temperature converter returns celsius times 9, divided by 5, plus 32, and is called with the argument 20 inside print. What does the program print?
After the four answers, I must briefly interpret each one: for P1, say which number goal and which number pages read hold during the call, and name the two local names that vanish when the call ends; for P2, say why swapping the arguments changes what prints, and name the kind of error the slip is; for P3, run the neighbor's original printing version, say what it prints and which exception type the last line of its error names, and say why changing print to return fixes it; for P4, say why the printed number ends in .0, then store what the call hands back in a name, print the name, and say what prints. I must then write a 3-5 sentence message to a neighbor whose garden program printed 15 and then stopped with an error, explaining in everyday words why the number seemed lost, how changing one word fixes it, and naming one limit or caveat. I must explain technical terms in everyday words.

SCORING CRITERIA: Score only evidence I supply: correct traces (40 points), reasoning about how Python runs a function (32 points), clarity for a non-programmer (16 points), and showing the trace and the run (12 points). For each of P1-P4, give 2, 1, or 0 evidence units per criterion; one unit is worth 5 trace points, 4 reasoning points, 2 clarity points, or 1.5 showing points. Sum all four problems within each criterion. Count my final message only with P4, not again with P1-P3.
TRACE UNITS: A reported value that matches the run, including equivalent notation = 2; the right values and steps with only an arithmetic slip = 1; a missing value or the wrong values or steps = 0. Do not penalize an alternative valid way of showing the trace.
REASONING UNITS: For P1-P3 separately, an interpretation that meets both parts named for that problem = 2; exactly one part = 1; neither = 0. For P4, the .0 explained AND the stored-value run reported AND a neighbor message with the fix and a named limit = 2. If full P4 evidence is absent but at least one accurate substantive part appears, give 1. No accurate reasoning = 0; naming a term alone does not earn a unit. An arithmetic slip alone is not a reasoning error.
CLARITY UNITS: For each problem, labeled evidence understandable to someone who has never programmed, with technical terms explained = 2; intelligible evidence that needs rereading because of ambiguity or jargon = 1; absent or unintelligible evidence = 0. Include the final message with P4 if submitted. Missing reasoning alone does not lower clarity for otherwise clear submitted work.
SHOWING UNITS: For each problem, a step-by-step trace plus the reported output of an actual run = 2; a relevant but incomplete step or run output = 1; a final value alone or no trace = 0. A visible trace stays checkable despite an arithmetic slip.

Do NOT invent grading rules.

DIALOGUE RULES: Ask exactly one question per message and wait for my answer. Start by asking for my complete first attempt. Build each next question from my exact words. Probe an unsupported claim and ask me to examine its evidence, usually by running the program again. Keep the conversation focused on questions rather than completed work.

ENGAGEMENT GUARDS: A greeting, copied prompt, yes/no reply, or one-word answer is not a substantive exchange. Do not flatter or accept agreement as evidence. Praise only a concrete move I made. If evidence is missing, say what is missing and ask for it. Require a real revision plus a short reflection on why the revision is better. Do not issue the report early.

EXIT CONDITION: Continue until at least five substantive exchanges have occurred AND I have supplied all four answers with their runs and brief interpretations AND written my message to the neighbor AND revised at least one trace or explanation AND reflected on the revision. Stop only after whichever requirement happens last.

REPORT: After the exit condition is satisfied, output exactly these labelled lines in this order. Replace X with the exact earned score; it may end in .5 and must not be rounded to a whole number. Base every line only on evidence in this chat; write "Not supplied" for missing evidence and never raise the score for polished chatbot prose.
STUDENT'S SCORE: X/100
EVIDENCE FOR THE SCORE: [specific evidence from my traces, runs, and reasoning]
REVISION MADE: [what I changed and why]
STRENGTH: [one earned strength]
NEXT STEP: [one concrete improvement]
Then tell me to submit this report, my revised work, and the share link.
COPY EVERYTHING ABOVE THIS LINE

Deliverables

Submit these three items in the assignment entry:

• your revised work with all four predictions and actual outputs, their brief interpretations, the run of your neighbor's original printing version, and the run of print(reading), and your message to your neighbor — written, or recorded as audio or video with a transcript, or as a labelled screen capture of your runs with a short note for each; every form is graded by the same scoring criteria;
• the coach's five-line report; and
• the conversation share link.

Submit in any accessible file type or as a link; a recorded response may be submitted as audio or video with a transcript, or as text.

Equivalent route (no AI required)

This route assesses the same Week 7 skills — predicting what a function call hands back, matching arguments to parameters by position, telling return from print and the None a printing function hands back, and naming which names live in a call's frame — for comparable time and effort, about 60 to 90 minutes, the same as the coached route. Complete the same four problems with your predictions and runs, the four brief interpretations, the run of your neighbor's original printing version, the run of print(reading), and the message to your neighbor. Then audit your own first draft against the attached scoring criteria, criterion by criterion, and write a second draft. Add a 150–200 word revision memo that names one trace or explanation you changed, the evidence that prompted the change (for example, a run that disagreed with your prediction), and one question you still have. Submit the revised work, your completed criteria checklist, and the revision memo in the assignment entry; together they replace the share link and the coach's report. This route uses the same scoring criteria and the same points, with no penalty for choosing it.

How you'll be graded

The full analytic rubric is attached to this assignment in Canvas.

Academic integrity and AI use

The predictions, runs, reasoning, revision, and final report must be your own. Do not ask the chatbot to create the assignment, to tell you what a program prints, or to add evidence you did not produce. Submit an honest share link from your own dialogue. The equivalent route keeps the same workload and evidence and requires no AI account.

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