Answer: Python Puzzler #1814

The answer is A. The program prints:

59

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
50	yes	50
45	no	50
59	yes	59
18	no	59
39	no	59

The code again

numbers = [50, 45, 59, 18, 39]
biggest = 0
for n in numbers:
    if n > biggest:
        biggest = n
print(biggest)