Answer: Python Puzzler #900

The answer is B. The program prints:

###
###

Checked by running the program for real.

The outer loop runs 2 times (one per row). Inside it, the inner loop adds 3 symbols to line. So you get 2 rows of 3.

A trace table follows the program step by step. Here’s this one:

row	line printed
0	###
1	###

for row in range(2):
    line = ""
    for col in range(3):
        line = line + "#"
    print(line)

Try it: change one number in the program and predict the new output before you run it.