Answer: Python Puzzler #3914

The answer is D. The program prints:

moo

This answer was checked by running the program for real.

Why?

A dictionary stores pairs: a key and its value. sounds["cow"] looks up the key ‘cow’ and gives back its value.

Trace table

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

keyvalue
duckquack
cowmoo
lionroar
owlhoot

The code again

sounds = {
    "duck": "quack",
    "cow": "moo",
    "lion": "roar",
    "owl": "hoot",
}
print(sounds["cow"])

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