Python Puzzler #241

Python Puzzler 241 card

Challenge type: Python Puzzlers  ·  Difficulty: ★☆☆☆☆ Easy peasy  ·  Topic: decisions

Read this Python program carefully. Don’t run it yet! Can you work out exactly what it prints?

Python puzzler 241 code
What does it print?
battery = 14
if battery > 15:
    print("Full speed ahead!")
elif battery > 10:
    print("Slow and steady.")
else:
    print("Time to recharge!")

Choose an answer

ChoiceOutput
A
Time to recharge!
B
Nothing is printed
C
Full speed ahead!
D
Slow and steady.
Need a hint?

Pretend you are the computer. Go through the program one line at a time, and write down every variable’s value on paper as it changes. Programmers call this a trace.

Grown-ups: Reading code and predicting what it does is a key programming skill. Once your child has chosen an answer, run the code in IDLE together to check.

For teachers and grown-ups

Skills practised: Code reading, tracing variables, and understanding Python syntax.

The big idea: Predicting a program's output before running it builds a solid mental model of how code works.

Questions to ask:

  • What is the value of each variable after every line?
  • Which line decides the output?
  • What small change would make it print something different?

Take it further: Children use a trace table on paper for the code, then run it in IDLE to check, and change one value to make a new puzzle for a friend.