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Entering in data using while

Q1. Enter this code into Python and get it working:

poem = []      #Create an empty list. Each element will be a line in the poem.
print('Write a poem .... ')
print('Press <ENTER> again to quit.')

line = input('Enter the first line >>> ') # initalise line
while line != '':      # while line is not empty
    poem.append(line)
    line = input('Please enter the next line >>> ')

print('\n')
print('Your poem is:')
for line in poem:
    print(line)

Q2. Explain how this block of code works:

line = input('Enter the first line >>> ') # initalise line
while line != '':      # while line is not empty
    poem.append(line)
    line = input('Please enter the next line >>> ')

Q3. Write a program that allows a user to keep entering in their favourite foods, until they enter -999. The program should print out their list of favourite foods.
Q4. Do some research. What is a 'sentinel' in programming? Identify the sentinel used in Q3.
Q5. Enter this code:

1    #Add up lots of numbers ...
2    print('Keep entering numbers. Enter -999 to quit')
3    temp = 0
4    total = 0
5    while temp != -999:
6        temp = float(input('Please enter a number >>> '))
7        total = total + temp
8    print('The total is ...',total)

 It should allow the user to keep entering in numbers, until they enter -999. It should then add up the numbers and display the total. The program doesn't work. Investigate why by dry-running the code using a trace table. Remember, only enter in a new value on a new line when that value actually changes. The trace table has been started for you. Enter the following data into the trace table: 17, 4, 5, -999 When you have identified the problem, correct it and test the program with your own values to check it works.

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