Answer: Python Puzzler #1671

The answer is A. The program prints:

56

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
34	yes	34
56	yes	56
21	no	56
27	no	56
30	no	56

The code again

numbers = [34, 56, 21, 27, 30]
biggest = 0
for n in numbers:
    if n > biggest:
        biggest = n
print(biggest)