Answer: Python Puzzler #1589

The answer is D. The program prints:

54

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
33	yes	33
30	no	33
12	no	33
54	yes	54
15	no	54

The code again

numbers = [33, 30, 12, 54, 15]
biggest = 0
for n in numbers:
    if n > biggest:
        biggest = n
print(biggest)