Chapter 8 Exercises¶

1. Fix the 5 syntax errors in the code below to print a countdown of the numbers from 10 to 0.

   counter = 10 while Counter > 0: Print(counter) counter = Counter + 1

2. The following code will loop infinitely. Make one change that will make it loop only 5 times.

   x = 5 while x > 0: print(x) x = x + 1

3. Make 5 changes to the code below to correctly print a count up from -10 to 0.

   output = "" x = -10 while x < 0 x = x - 1 output = output + str(x) + " " print(output)

4. Fix the errors in the code below so that it uses 2 loops to print 8 lines of *.

   for x in range(1, 2) y = 0 while y < 4: print("*") y = y + 1

5. Finish lines 1 and 5 so that the following code correct prints all the values from -5 to -1.

   output = ?? x = -5 while x < 0: output = output + str(x) + " " x = ?? print(output)

6. Complete the code on lines 4 and 6 so that it prints the number 6.

   x = 3 i = 0 while i < 3: x = ?? i = i + 1 print(??)

7. The code below is supposed to print an estimate of the square root. But, the indention is wrong on 4 lines. Fix it.

   target = 6 guess = 2 guess_squared = guess * guess while abs(target - guess_squared) > 0.01: closer = target / guess guess = (guess + closer) / 2.0 guess_squared = guess * guess print("Square root of", target,"is", guess)

8. The function currently takes a start and stop argument and uses a for loop to find the sum of all the numbers between them (inclusive). Change the for loop to a while loop while still using the parameters.

   def sum_func(start, stop): sum = 0 for num in range(start, stop + 1): sum = sum + num return sum print(sum_func(1, 10))

9. The program below is supposed to print the times tables for 1 to 3, but there are 5 errors. Fix the errors.

   for x in range(1, 3): for y in range(1, 10) print(str(x) + " * " str(y) + " = " x * y)

10. Rewrite the code that prints the times tables for 1 to 3 using a while loop and a for loop instead of two for loops.

    for x in range(1, 4): for y in range(1, 11): print(str(x) + " * " + str(y) + " = " + str(x * y))

11. Rewrite the following code to use a while loop instead of a for loop.

    product = 1 # Start with multiplication identity numbers = range(1, 11) for number in numbers: product = product * number print(product)

12. Fix the errors so that the code gets the average of the numbers from 1 to 10. You should get 5.5 when you are finished.

    sum = 10 x = 0 while x < 11: sum = x x = x + 1 average = sum / 2 print(average)

13. Rewrite the following code to use a while loop instead of a for loop.

    # Step 1: Initialize accumulator product = 1 # Initialize to multiplication identity # Step 2: Get data numbers = range(10, 21, 2) # Step 3: Loop through the data for number in numbers: # Step 4: Accumulate product = product * number # Step 5: Process result print(product)

14. The code below currently enters a loop where it keeps printing “Even”. Fix the code so that it prints “Even” and “Odd” for numbers 0 to 9.

    number = 0 while number < 10: while number % 2 == 0: print("Even") while number % 2 != 0: print("Odd") number = number + 1

15. Fix the code below so that it will take numbers as input until you enter a negative number and then will return the average of the numbers.

    sum = ?? count = ?? message = "Enter an integer or a negative number to stop" value = input(message) while int(value) > 0: print("You entered " + value) sum = ?? + ?? count = ?? value = ?? print("The sum is: " + str(sum) + " the average is: " + str(sum / count))

16. Fix and change the code so it prints a table of division instead of multiplication for -10 to -1.

    for x in range(0, 11) for y in range(1, 11): print(str(x) + " * " + str(y) + " = " + str(x * y))

17. Create a function to calculate and return the sum of all of the even numbers from 0 to the passed number (inclusive) using a while loop.

18. Write a procedure that takes a user input and keeps asking for a user input until the input is “Hello”. If the input is not “Hello”, it should print “This is your n wrong try.” where n is the number of times they have put an input in. If they type “Hello”, the procedure should print “Success!”. Hint: != means does not equal

19. Create a procedure to print stars and spaces in a roughly square pattern and have it take as input the number of stars on a side. Use a nested loop to do this.

20. Write a procedure that takes an int argument and uses a while loop to create a right-triangle like shape out of *. The first row should have 1 star and the last should have n stars where n is the argument passed.