Answer: Python Puzzler #3909

The answer is D. The program prints:

34

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
28	yes	28
11	no	28
15	no	28
34	yes	34
31	no	34

The code again

numbers = [28, 11, 15, 34, 31]
biggest = 0
for n in numbers:
    if n > biggest:
        biggest = n
print(biggest)