Answer: Python Puzzler #848

The answer is B. The program prints:

6
2
Lift off!

Why?

The loop keeps going while count > 0. Each time round it prints count, then takes away 4. When count reaches -2, the condition is false, the loop stops, and the last line prints.

Trace table

A trace table follows the program step by step. Here’s this one:

count	count > 0?	new count
6	yes	2
2	yes	-2
-2	no (stop)

The code again

count = 6
while count > 0:
    print(count)
    count = count - 4
print("Lift off!")