Control Structures & Iterables — Code Cards (Classroom Version)¶

Try me¶

How to use¶

Each card below mirrors the A4 activity prompt. First try to complete the exercise by yourself, predict the output or find the bug before running.
Then run the code cell to verify, or run the Fix cell (when provided) to see a correct version.
Keep explanations short and schematic (what/why). ### Rendering Gemini into an interactive AI tutor
If you need help, hints, or extra exercises from AI, use the following prompt to convert it into an AI-tutor

You are a **coding tutor** for Python in Jupyter/Colab. Follow the **course motto** “do not give up learning.”

### Role & Goals
- Use **Socratic guidance** and **test-first thinking** to help me solve problems myself.
- Help me read errors, reason about state, and make small, safe iterations.

### Strict Rules
1) **Do not** provide full working solutions or paste complete functions/programs.
   - You may show **tiny illustrative fragments (≤3 lines)** or **pseudo-code with TODOs**, but not a drop-in answer.
2) Prefer **questions over answers**; offer **one small next step** at a time.
3) When debugging, explain **what the traceback says**, give **2–3 hypotheses**, and propose the **smallest diff** in *plain English* first.
4) Encourage **TDD**: ask me to write/assert a test, predict, run, and report outputs.
5) Keep responses concise (≈120–150 words) unless I ask for a deeper explanation or code review.
6) Ask me to **run code and share results**; adapt based on the output.
7) If I request the full solution, remind me of the rules and offer a **higher-tier hint** instead.
8) When I finalize an exercise, reinforce learning lessons and suggest additional exercises

### Interaction Loop (use this structure)
- **Restate goal:** what I’m trying to accomplish in one line.
- **Diagnose:** key assumption to check or error to interpret.
- **Hint (tiered):**
  - Tier 1: Conceptual nudge (no code).
  - Tier 2: Directed hint (identify line/construct to change).
  - Tier 3: Pseudo-code with TODOs or a **1–3 line** pattern (still not a full solution).
- **Next action:** one concrete step for me to try now.
- **Ask back:** what to run/paste (output, test result, or traceback).

### When reviewing my code
- Comment on **correctness, clarity, naming, and complexity (big-O)**.
- Suggest **tests** I’m missing (boundaries, empty cases, error paths).

### Safety & Ethics
- No secrets or private data in prompts.
- avoid library functions/APIs unless I ask.

Stay in tutor mode for the whole session.

Basic control structures - If-else statements¶

Card IF-1 — Predict the output¶

x = 20
if x < 20:
    msg = "A"
elif x <= 20:
    msg = "B"
else:
    msg = "C"
print(msg)

Question: What is printed?

[ ]:

# Card IF-1 — run to check
x = 20
if x < 20:
    msg = "A"
elif x <= 20:
    msg = "B"
else:
    msg = "C"
print(msg)  # expected: B

Card IF-2 — Predict the output¶

x = 19
msg = "X"
if x < 20:
    msg = "A"
if x < 19:
    msg = "B"
else:
    msg = "C"
print(msg)

Question: What is printed?

[ ]:

# Card IF-2 — run to check
x = 19
msg = "X"
if x < 20:
    msg = "A"
if x < 19:
    msg = "B"
else:
    msg = "C"
print(msg)  # expected: C (else binds to second if)

Card IF-3 — Predict the output¶

temp = 22
if temp > 20:
    if temp < 25:
        res = "A"
else:
    res = "B"
print(res)

Question: What is printed?

[ ]:

# Card IF-3 — run to check
temp = 22
if temp > 20:
    if temp < 25:
        res = "A"
else:
    res = "B"
print(res)  # expected: A (nested if is True; outer else is skipped entirely)

Card IF-4 — Code Wizard (Optimize the branching)¶

Original:

temp = 22
if temp > 20:
    if temp < 25:
        res = "A"
else:
    res = "B"
print(res)

Task: Rewrite with a clear if/elif/else chain.

[ ]:

# Card IF-4 — one possible optimization
temp = 22
if temp <= 20:
    res = "B"
elif temp < 25:
    res = "A"
else:
    res = "B"
print(res)  # clearer mutually-exclusive branches

Card IF-5 — Predict the output¶

score = 90
if score >= 80:
    grade = "A"
elif score >= 90:
    grade = "A+"
else:
    grade = "B"
print(grade)

Question: What is printed?

[ ]:

# Card IF-5 — run to check
score = 90
if score >= 80:
    grade = "A"
elif score >= 90:
    grade = "A+"
else:
    grade = "B"
print(grade)  # expected: A (first true branch wins)

2) while loops — Human Calculator & Code Detective¶

Card WH-1 — Code Detective (Find the bug)¶

Buggy code (indentation error):

i = 0
while i < 5:
  i += 1
    print(i)
  if i % 2 == 0:
    continue

Task: Fix indentation so it runs and behaves as intended.

[ ]:

# Card WH-1 — Fixed version
i = 0
while i < 5:
    i += 1
        print(i)
    if i % 2 == 0:
        continue

Card WH-2 — Predict the output¶

i = 3
while i > 0:
    print(i, end="")
    i -= 1
print("done")

Question: What is printed?

[ ]:

# Card WH-2 — run to check
i = 3
while i > 0:
    print(i, end="")
    i -= 1
print("done")  # expected: 321done

Card WH-3 — Human Calculator¶

n = 0
while True:
    n += 1
    if n == 3:
        continue
print(n)

Question: How many times does the loop run?

Card WH-4 — Predict the output¶

i, s = 0, 0
while i < 5:
  i += 1
  if i % 2 == 0:
    continue
  s += i
print(s)

Question: What is printed?

[ ]:

# Card WH-4 — run to check
i, s = 0, 0
while i < 5:
    i += 1
    if i % 2 == 0:
        continue
    s += i
print(s)

3) for loops — Human Calculator & Code Detective¶

Card FOR-1 — Predict the output¶

names = ["A","B"]
for i, n in enumerate(names, start=1):
    print(i, n)

Question: What is printed?

[ ]:

# Card FOR-1 — run to check
names = ["A","B"]
for i, n in enumerate(names, start=1):
    print(i, n)

Card FOR-2 — Predict the output¶

for x in [0,1,2]:
    if x:
        continue
    print(x)

Question: What is printed?

[ ]:

# Card FOR-2 — run to check
for x in [0,1,2]:
    if x:
        continue
    print(x)

Card FOR-3 — Predict the output¶

for i in range(5):
    print(2**i)

Question: What is printed?

[ ]:

# Card FOR-3 — run to check
for i in range(5):
    print(2**i)

Card FOR-4 — Code Detective (Find the bug)¶

Prompt comment:

# print odd numbers from 1 to 5 [1, 3, 5]
for i in range(5, 1, 1):
    print(i)

Task: Fix the loop to match the comment.

[ ]:

# Fix the loop to match the comment. Hint: check range arguments
for i in range(5, 1, 1):
    print(i)  # 1, 3, 5

Notes

if/elif/else: first true branch executes; else binds to the nearest unmatched if.
while True without break never terminates.
continue skips to the next iteration; break exits the loop.
enumerate(iterable, start=1) yields (index, item).
range(start, stop, step): stop is exclusive.

Extra exercises¶

Card EX-1 — Predict the output¶

for i in range(3):
    for j in range(2):
        if i == j:
            print(i, j)

Question: What is printed?

[ ]:

for i in range(3):
    for j in range(2):
        if i == j:
            print(i, j)

Card EX-2 — Code Wizard (Optimize the loop)¶

Task: Fix the code so that “Done” is printed when the loop completes, without unnecessary logic. Explain your changes.

i = 0
while i < 5:
    print(i)
    i += 1
    if i == 5:
        print("Done")
        break

[ ]:

i = 0
while i < 5:
    print(i)
    i += 1
    if i == 5:
        print("Done")
        break

Card EX-3 — Human Calculator (Predict the output)¶

What is printed?

s = 0
for i in range(1, 6, 2):
    if i % 2 == 0:
        s += i
    else:
        s += i * 2
print(s)

[ ]:

s = 0
for i in range(1, 6, 2):
    if i % 2 == 0:
        s += i
    else:
        s += i * 2
print(s)

Card EX-4 — Human Calculator (Predict the output)¶

What is printed?

a = [1, 2, 3, 4, 5, 6, 7]
print(a[::-2])

[ ]:

a = [1, 2, 3, 4, 5, 6, 7]
print(a[::-2])

Card EX-5 — Code Wizard (Fix slicing)¶

Task: Fix the code to print [“B”, “o”, “n”, “e”] using as much defaults as possible

b = ["B", "r", "o", "w", "n", "i", "e"]
print(b[1:7:2])

[5]:

b = ["B", "r", "o", "w", "n", "i", "e"]
print(b[1:7:2])

['r', 'w', 'i']