Answer: Python Puzzler #3809

The answer is D. The program prints:

47

This answer was checked by running the program for real.

Why?

The loop remembers the biggest number it has seen so far, and replaces it whenever it finds a bigger one. This is how computers find the maximum.

Trace table

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

n	n > biggest?	biggest
36	yes	36
34	no	36
47	yes	47
40	no	47
31	no	47

The code again

numbers = [36, 34, 47, 40, 31]
biggest = 0
for n in numbers:
    if n > biggest:
        biggest = n
print(biggest)