Week 1 — Predict, Run, Explain: Your First Python Traces

Assignment 1 of the term — predict what short Python lines print, run them to check, read two error messages from their last lines, 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 week's lecture tutorial, quiz, discussion, and Coding Lab practise the same ideas from other angles; this assignment is where you put them together.

The task

A relative watched you run your first Python line and said, "Your computer got the math wrong: 2 plus 3 is 5, and 5 times 4 is 20, but it printed 14." Your job is to check that claim the way a programmer would: predict each line before you run it, run it in a free browser Python runner, and explain what Python actually did. All four programs are illustrative.

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

1. What does the one-line Python program print(2 + 3 * 4) print when it runs?
2. What does the one-line Python program print((2 + 3) * 4) print when it runs?
3. A study room has two tables with 4 chairs each plus 3 extra chairs, and the line print(3 + 2 * 4) counts them. What does it print?
4. What does the one-line Python program print(10 / 2) print when it runs?

Beside each answer, add one brief interpretation:

• Problem 1: name operator precedence as the reason for the output, and explain why 20 is the tempting wrong prediction.
• Problem 2: say what the parentheses changed, and compare this output with your Problem 1 output.
• Problem 3: say which line, print(3 + 2 * 4) or print((3 + 2) * 4), matches the real chair count, and explain why both lines run without an error although only one of them fits the room.
• Problem 4: explain the decimal point in the output in one sentence (Week 2 explains it fully). Then run these two broken programs and, for each, read the last line of the error message, name the error type, and say whether line 1 printed before it stopped:

print("Reading log: day 1")
Print("Goal: 300 pages")

print("Reading log: day 1")
print("Goal: 300 pages"

Explain it to a non-programmer

Write a 3–5 sentence message to your relative that explains, in everyday words, why the computer printed 14 and did not get the math wrong. Use the idea that the computer does exactly what you wrote, not what you meant, say how parentheses would have produced 20, and name one limit or caveat, such as the fact that the rule only tells you what Python does, not what you intended. Explain any technical term in everyday words. More than one good message is possible.

For a different, ungraded example, imagine a coworker who typed 8 − 2 × 3 into a phone calculator, expected 18, and got 2. Model message: "The calculator did not make a mistake. It follows a fixed rule: multiply before you subtract, so it worked out 2 × 3 = 6 first and then 8 − 6 = 2. If you meant to subtract first, put parentheses around 8 − 2. The rule tells you what the calculator will do; it cannot guess what you meant, so check the grouping before you trust a total."

Use that pattern for your relative'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 relative before opening a chatbot. Run every line 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 tracing short programs, operator precedence, and reading error messages from their last line. 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 programs are illustrative. For each one I write a prediction first, then run the line and report the actual output beside it.
PROBLEM P1: What does the one-line Python program print(2 + 3 * 4) print when it runs?
PROBLEM P2: What does the one-line Python program print((2 + 3) * 4) print when it runs?
PROBLEM P3: A study room has two tables with 4 chairs each plus 3 extra chairs, and the line print(3 + 2 * 4) counts them. What does it print?
PROBLEM P4: What does the one-line Python program print(10 / 2) print when it runs?
After the four answers, I must briefly interpret each one: for P1, name operator precedence as the reason for the output, and explain why 20 is the tempting wrong prediction; for P2, say what the parentheses changed, and compare this output with my P1 output; for P3, say which line, print(3 + 2 * 4) or print((3 + 2) * 4), matches the real chair count, and explain why both lines run without an error although only one of them fits the room; for P4, explain the decimal point in the output in one sentence, then run two broken programs and, for each, read the last line of the error message, name the error type, and say whether line 1 printed before it stopped. The first broken program is print("Reading log: day 1") followed by Print("Goal: 300 pages"). The second is print("Reading log: day 1") followed by print("Goal: 300 pages" with no closing parenthesis. I must then write a 3-5 sentence message to a relative who thinks the computer got the math wrong when print(2 + 3 * 4) printed 14, explaining in everyday words why it did not, saying how parentheses would have produced 20, 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 code (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 and the two broken programs only with P4, not again with P1-P3.
TRACE UNITS: A printed value that matches the run, including equivalent notation = 2; the right values and order of operations with only an arithmetic slip = 1; a missing result or the wrong values or order = 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 decimal output explained AND both broken programs read from the last line with each error type named and whether line 1 printed AND a relative message with the parentheses point 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 result = 1; a result 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 line 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 relative 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 two error readings, and your message to your relative — 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 1 skills — predicting what a short line prints and checking it by running it, explaining operator precedence and parentheses, and reading an error message from its last line to tell a SyntaxError from a NameError — 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 two error readings, and the message to your relative. 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 line 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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