Loops Practice

These questions follow Loops. A loop is a bargain with the computer: you describe one round precisely, it does all of them.

Questions

1. Which of these needs a loop — (a) locking one door, (b) handing back 28 quizzes, (c) wearing boots if it rains?
2. Predict the output — how many lines, and what is on each?

   for number in range(4):
       print(number)

3. Trace total through every round, then predict what prints.

   total = 0
   for number in range(1, 4):
       total = total + number
   print(total)

4. Find the bug. This countdown never reaches lift-off — or ends.

   count = 3
   while count > 0:
       print("T-minus", count)

5. Write a loop that prints 10 down to 1 — countdown style.
6. Challenge. Keep asking Password? until the user types sesame, then print how many attempts were needed.

Answers

Answer 1

Only (b) — one action, 28 repeats. (a) is a single step, and (c) is a decision: a job for a conditional, not a loop.

Answer 2

Four lines: 0, 1, 2, 3. range(4) starts at 0 and stops before 4 — four numbers, none of them 4. Everyone trips on this.

Answer 3

total goes 0, then 1, then 3, then 6 — range(1, 4) supplies 1, 2, 3. Only 6 prints: the print sits outside the loop.

Answer 4

Nothing inside the loop ever changes count, so T-minus 3 prints forever. Add count = count - 1 inside — it ends in three lines.

Answer 5

for number in range(10, 0, -1): then print(number) beneath. The third value steps by -1; the stop value 0 is never printed.

Answer 6

Start attempts = 0 and word = "". Then while word != "sesame": read word = input("Password? ") and add 1 to attempts inside the loop. Print attempts after — the loop only ends on success.

Curriculum connection

C2.4

write programs that include sequential, selection, and repeating events

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C1.5

identify and explain situations in which conditional and repeating structures are required

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