Week 9 — Lists, Methods, and the Backup That Was Not

Assignment 8 of the term — read and change lists, predict what each list method hands back, tell an alias from a copy, 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 Week 7's functions: a list method, like a function with no return, can do real work and still hand back None. 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 friend who directs a community choir keeps the night's songs in a short program: setlist = ["intro", "anthem", "lullaby", "march", "waltz", "finale"]. Before cutting two songs, your friend wrote backup = setlist to keep the full list safe, then ran setlist.remove("march") and setlist.remove("waltz"). Later, your friend printed backup and found songs missing, and says, "My backup lost songs I never touched." 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; Problem 1 uses this week's reading log, whose daily list is [12, 40, 25, 0, 33, 17, 27].

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 daily list holds 7 days whose pages total 154. What does print(total / len(daily)) show?
2. A list starts as a = [1, 2], and then a.append([3, 4]) runs. How many items does len(a) report?
3. Your friend's setlist holds 6 songs, backup = setlist runs, and then two setlist.remove calls delete 2 songs. How many songs does len(backup) report?
4. A loop walks minutes = [0, 0, 90, 0, 85] and calls minutes.remove(0) for each 0 it sees. How many items does len(minutes) report afterward?

Beside each answer, add one brief interpretation:

• Problem 1: explain why the line shows a decimal point, and run the reading log's biggest-day loop to say what it prints and why it starts at daily[0].
• Problem 2: explain why append added only one item, then run the same program with extend instead and report the length.
• Problem 3: explain why the backup changed, then change backup = setlist to backup = setlist[:], run it, and report the length and what backup is setlist prints.
• Problem 4: explain why one 0 survives the loop, then run one of this week's two cures and report what it prints.

Explain it to a non-programmer

Write a 3–5 sentence message to your friend that explains, in everyday words, why the backup lost two songs and how changing one line keeps the full list safe. Use the idea that backup = setlist gives one list a second name, and name one limit or caveat, such as the fact that a copy made before the cuts will not pick up songs added later. Explain any technical term in everyday words. More than one good message is possible.

For a different, ungraded example, imagine a roommate whose program sorted a grocery list with groceries = groceries.sort() and then printed None instead of the list. Model message: "The sort command does its work right on the list and then hands back nothing, which Python calls None. Your line stored that nothing back under the list's name, so the sorted list was lost. Writing the sort on its own line, without the equals sign, keeps the list and puts it in order. One catch: that changes the original order for good, so if you still need the old order, ask for a sorted copy instead."

Use that pattern for your friend'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 friend 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 lists, list methods, aliases and copies, and loops over lists. 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 daily list holds 7 days whose pages total 154. What does print(total / len(daily)) show?
PROBLEM P2: A list starts as a = [1, 2], and then a.append([3, 4]) runs. How many items does len(a) report?
PROBLEM P3: A setlist holds 6 songs, backup = setlist runs, and then two setlist.remove calls delete 2 songs. How many songs does len(backup) report?
PROBLEM P4: A loop walks minutes = [0, 0, 90, 0, 85] and calls minutes.remove(0) for each 0 it sees. How many items does len(minutes) report afterward?
After the four answers, I must briefly interpret each one: for P1, explain why the line shows a decimal point, and run the biggest-day loop to say what it prints and why it starts at the first item; for P2, explain why append added only one item, then run the same program with extend and report the length; for P3, explain why the backup changed, then change the line to a full slice, run it, and report the length and what the is test prints; for P4, explain why one 0 survives the loop, then run one of the two cures and report what it prints. I must then write a 3-5 sentence message to a friend whose choir backup lost two songs, explaining in everyday words why the backup changed, how one changed line keeps the full list safe, 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 treats a list (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, why one 0 survives AND the run of one cure AND a friend message with the slice 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 friend 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 runs of the biggest-day loop, the extend version, the full-slice backup, and one cure for the loop trap, and your message to your friend — 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 9 skills — walking a list for an average and a maximum, predicting what a list method hands back and how many items a list holds after it runs, telling an alias from a copy, and repairing a loop that changes the list it walks — 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 runs of the biggest-day loop, the extend version, the full-slice backup, and one cure for the loop trap, and the message to your friend. 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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