Python Unit 7: Loops Practice Questions

Practice questions for Python Unit 7 on loops (while and for loops, iteration, and loop tracing), with explanations for every answer.

150 questions · Python Programming · by Study Foxy

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Questions

1. What does this program print?\n\nn = 1\nwhile n < 20:\n n = n * 2\nprint(n)

   • 32
   • 16
   • 20
   • 64

2. What does this program print?\n\nn = 1\nwhile n < 20:\n print(n)\n n = n * 2

   • 1\n2\n4\n8\n16
   • 2\n4\n8\n16\n32
   • 1\n2\n4\n8\n16\n32
   • 2\n4\n8\n16

3. What does this program print?\n\ncount = 5\nwhile count > 0:\n count = count - 2\nprint(count)

   • -1
   • 0
   • 1
   • -2

4. How many times does the loop body run? The program prints the answer.\n\nk = 0\ntimes = 0\nwhile k < 17:\n k = k + 4\n times = times + 1\nprint(times)

   • 5
   • 4
   • 6
   • 17

5. What does this program print?\n\nx = 50\nwhile x < 10:\n print(x)\n x = x + 1\nprint('end')

   • end
   • 50\nend
   • Nothing is printed
   • 50

6. Which loop never stops?

   • x = 1\nwhile x != 10:\n x = x + 2
   • x = 1\nwhile x < 10:\n x = x + 2
   • x = 1\nwhile x != 9:\n x = x + 2
   • x = 20\nwhile x < 10:\n x = x + 2

7. The user types hi, yo, stop. What is printed?\n\nword = input('Word: ')\nwhile word != 'stop':\n print(f'got {word}')\n word = input('Word: ')

   • Word: hi\ngot hi\nWord: yo\ngot yo\nWord: stop
   • Word: hi\nWord: yo\nWord: stop
   • Word: hi\ngot hi\nWord: yo\ngot yo\nWord: stop\ngot stop
   • got hi\ngot yo

8. The loop body never asks for a new word. The user types hi. What happens?\n\nword = input('Word: ')\nwhile word != 'stop':\n print(f'got {word}')

   • got hi prints forever
   • SyntaxError
   • got hi prints once
   • It asks again

9. The user types 12, 123456, 4821. What is printed?\n\npin = int(input('PIN (4 digits): '))\nwhile pin < 1000 or pin > 9999:\n print('Try again')\n pin = int(input('PIN (4 digits): '))\nprint('Saved')

   • PIN (4 digits): 12\nTry again\nPIN (4 digits): 123456\nTry again\nPIN (4 digits): 4821\nSaved
   • Try again\nTry again\nSaved
   • PIN (4 digits): 12\nTry again\nPIN (4 digits): 123456\nSaved
   • PIN (4 digits): 12\nTry again\nPIN (4 digits): 123456\nTry again\nPIN (4 digits): 4821\nTry again\nSaved

10. A loop must keep asking while the rating is outside 1-5. Which condition goes after while?

    • rating < 1 or rating > 5
    • rating < 1 and rating > 5
    • rating >= 1 and rating <= 5
    • rating > 1 or rating < 5

11. What does this program print?\n\ntotal = 0\nn = 1\nwhile n <= 4:\n total = total + n\n n = n + 1\nprint(total)

    • 10
    • 6
    • 4
    • 15

12. What does this program print?\n\nx = 100\nsteps = 0\nwhile x > 1:\n x = x // 2\n steps = steps + 1\nprint(steps)

    • 6
    • 50
    • 7
    • 5

13. What does this program print?\n\nx = 2\nwhile x < 30:\n x = x * x\nprint(x)

    • 256
    • 30
    • 64
    • 16

14. Savings grow 10% a year. How many years until the balance reaches 150?\n\nbalance = 100\nyears = 0\nwhile balance < 150:\n balance = balance * 1.1\n years = years + 1\nprint(years)

    • 5
    • 6
    • 4
    • 50

15. What happens when this runs?\n\nsecret = 7\nguess = 0\ntries = 0\nwhile guess != secret:\n guess = guess + 3\n tries = tries + 1\nprint(tries)

    • It never ends: guess skips 7
    • It prints 3, then stops
    • It prints 7, then stops
    • It prints 2, then stops

16. What does this program print?\n\nn = 10\nwhile n > 0:\n print(n)\n n = n - 4

    • 10\n6\n2
    • 6\n2
    • 10\n6
    • 10\n6\n2\n-2

17. What does this program print?\n\nn = 3\nwhile n > 0:\n n = n - 1\n print(n)

    • 2\n1\n0
    • 3\n2\n1\n0
    • 3\n2\n1
    • 2\n1

18. What does this program print?\n\nn = 3\nwhile n > 0:\n print(n)\n n = n - 1\nprint('after', n)

    • 3\n2\n1\nafter 0
    • 2\n1\n0\nafter 0
    • 3\n2\n1\nafter 1
    • 3\n2\n1\n0\nafter 0

19. Which task needs a while loop rather than a for loop?

    • Keep asking for a password until it is correct
    • Print every whole number from 1 up to 100
    • Print each of the 3 options on a fixed menu
    • Add up exactly 5 test scores the user types

20. What does this program print?\n\nlevel = 1\nxp = 0\nwhile xp < 50:\n xp = xp + 15\n level = level + 1\nprint(level, xp)

    • 5 60
    • 4 60
    • 4 45
    • 5 50

21. A training loop halves the error each epoch. What prints?\n\nerror = 8.0\nepochs = 0\nwhile error > 1:\n error = error / 2\n epochs = epochs + 1\nprint(epochs, error)

    • 3 1.0
    • 4 0.5
    • 8 1.0
    • 3 2.0

22. The loop condition is error >= 1. What prints?\n\nerror = 8.0\nepochs = 0\nwhile error >= 1:\n error = error / 2\n epochs = epochs + 1\nprint(epochs, error)

    • 4 0.5
    • 3 1.0
    • 4 1.0
    • 5 0.25

23. The user types 5, 8, -2, 0. What is printed?\n\ntotal = 0\nnum = int(input('n: '))\nwhile num != 0:\n total = total + num\n num = int(input('n: '))\nprint(total)

    • n: 5\nn: 8\nn: -2\nn: 0\n11
    • n: 5\nn: 8\nn: -2\nn: 0\n13
    • n: 5\nn: 8\nn: -2\n11
    • 11

24. A loop reads numbers until the user types 0. That 0 isn't real data; it only signals stop. What is that kind of value called?

    • A sentinel value
    • A loop variable
    • A Boolean flag
    • An accumulator

25. What does this program print?\n\nn = 5\nfact = 1\nwhile n > 1:\n fact = fact * n\n n = n - 1\nprint(fact)

    • 120
    • 20
    • 60
    • 24

26. What does this program print?\n\nx = 1\nwhile x < 10:\n x = x + 3\n if x == 7:\n print('seven')\nprint(x)

    • seven\n10
    • seven\nseven\n10
    • seven
    • 10

27. A while loop checks its condition before every pass, including the first.

    True or false

28. What does this program print?\n\nn = 0\nwhile n * n < 30:\n n = n + 1\nprint(n)

29. What does this program print?\n\nn = 10\nsteps = 0\nwhile n != 1:\n if n % 2 == 0:\n n = n // 2\n else:\n n = 3 * n + 1\n steps = steps + 1\nprint(steps)

30. Which tasks are a good fit for a while loop?

    • Re-prompt until the user enters valid input
    • Run a game until the player quits
    • Print the numbers 1 to 10
    • Process exactly 30 student records from a class roster

31. What does this program print?\n\nfor i in range(3, 8):\n print(i)

    • 3\n4\n5\n6\n7
    • 0\n1\n2\n3\n4
    • 3\n4\n5\n6\n7\n8
    • 4\n5\n6\n7

32. What does this program print?\n\nfor i in range(0, 12, 4):\n print(i)

    • 0\n4\n8
    • 0\n4\n8\n12
    • 4\n8
    • 0\n3\n6\n9

33. What does this program print?\n\nfor i in range(9, 0, -3):\n print(i)

    • 9\n6\n3
    • 6\n3\n0
    • Nothing is printed
    • 9\n6\n3\n0

34. What does this program print?\n\nfor i in range(5, 5):\n print(i)\nprint('done')

    • done
    • 5\ndone
    • 0\ndone
    • Nothing is printed

35. What does this program print?\n\nfor i in range(1, 10, 2):\n print(i)

    • 1\n3\n5\n7\n9
    • 2\n4\n6\n8
    • 1\n3\n5\n7\n9\n11
    • 1\n3\n5\n7

36. Which program prints 2 4 6 8 10 (one per line)?

    • for i in range(2, 11, 2):\n print(i)
    • for i in range(1, 11, 2):\n print(i)
    • for i in range(2, 10, 2):\n print(i)
    • for i in range(0, 10, 2):\n print(i)

37. Which program prints 5 4 3 2 1 (one per line)?

    • for i in range(5, 0, -1):\n print(i)
    • for i in range(5, 1, -1):\n print(i)
    • for i in range(5, 0):\n print(i)
    • for i in range(1, 6):\n print(i)

38. What does this program print?\n\ncount = 0\nfor i in range(4, 20, 5):\n count = count + 1\nprint(count)

    • 4
    • 5
    • 3
    • 16

39. What does this program print?\n\ntotal = 0\nfor i in range(1, 6):\n total = total + i\nprint(total)

    • 15
    • 10
    • 6
    • 21

40. The print is inside the loop. What prints?\n\ntotal = 0\nfor i in range(1, 6):\n total = total + i\n print(total)

    • 1\n3\n6\n10\n15
    • 15\n15\n15\n15\n15
    • 15
    • 1\n2\n3\n4\n5

41. What does this program print?\n\nproduct = 1\nfor i in range(1, 5):\n product = product * i\nprint(product)

    • 24
    • 10
    • 120
    • 0

42. product starts at 0. What prints?\n\nproduct = 0\nfor i in range(1, 5):\n product = product * i\nprint(product)

    • 0
    • 10
    • 24
    • 1

43. The user types 80, 90, 100. What is printed?\n\ntotal = 0\nfor i in range(3):\n total = total + int(input('Score: '))\nprint(total / 3)

    • Score: 80\nScore: 90\nScore: 100\n90.0
    • Score: 80\nScore: 90\nScore: 100\n270
    • Score: 80\nScore: 90\nScore: 100\n90
    • 90.0

44. What does this program print?\n\ns = ''\nfor i in range(3):\n s = s + 'ab'\nprint(s)

    • ababab
    • abababab
    • ab
    • ab\nab\nab

45. What does this program print?\n\ns = ''\nfor i in range(1, 4):\n s = s + str(i)\nprint(s)

    • 123
    • 0123
    • 1\n2\n3
    • 6

46. Each new piece is added on the left. What prints?\n\ns = ''\nfor i in range(1, 4):\n s = str(i) + s\nprint(s)

    • 321
    • 1
    • 6
    • 123

47. What does this program print?\n\nfor i in range(3):\n print('hi')\nprint(i)

    • hi\nhi\nhi\n2
    • hi\nhi\nhi\n3
    • hi\nhi\nhi
    • hi\nhi\nhi\nNameError

48. What does this program print?\n\ncount = 0\nfor i in range(10):\n if i % 3 == 0:\n count = count + 1\nprint(count)

    • 4
    • 9
    • 3
    • 10

49. The user types 4, 11, 7. What is printed?\n\nlargest = 0\nfor i in range(3):\n n = int(input('n: '))\n if n > largest:\n largest = n\nprint(largest)

    • n: 4\nn: 11\nn: 7\n11
    • 11
    • n: 4\nn: 11\nn: 7\n22
    • n: 4\nn: 11\nn: 7\n7

50. The user types -4, -11, -7. What is printed?\n\nlargest = 0\nfor i in range(3):\n n = int(input('n: '))\n if n > largest:\n largest = n\nprint(largest)

    • n: -4\nn: -11\nn: -7\n0
    • n: -4\nn: -11\nn: -7\n-4
    • n: -4\nn: -11\nn: -7\n-7
    • n: -4\nn: -11\nn: -7\n-11

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