Answer: Python Puzzler #1709

The answer is D. The program prints:

55

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
13	yes	13
9	no	13
45	yes	45
55	yes	55
34	no	55

The code again

numbers = [13, 9, 45, 55, 34]
biggest = 0
for n in numbers:
    if n > biggest:
        biggest = n
print(biggest)