Rover’s energy helper can calculate a value. Your job is to send that value back to the caller, store it, and display the result.
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A separate worked story shows real return and print events.
◇ Your mastery goalM16 · Returned values
Complete all 3 required tasks with a correct prediction, an inspected trace and an explanation that shows the concept. At least 2 must be independent checks, without answer-level help.
Rover has 12 energy units and a trip costs 5. Build a helper that returns the energy left. Rover must keep the remaining energy on the dashboard.
Read the inputs
battery12 charge unitscost5 charge units spent
Mission: calculate the remaining charge by passing both values to energy_left.
Predict before you run
Follow one value through the helper, the assignment, and the final print. Write None when a call sends no value back. The final printed value may be None even if the helper displayed a number inside its body.
Build the helper
Write a function that returns the battery charge minus the cost. Call it with the mission’s values, assign the returned value to remaining, then print remaining.
Allowed here: one energy_left(charge, cost) function with one return or print statement, a call, an assignment to remaining, and print(remaining).
Help for this puzzleStart with a nudge. Open an example or solution only when you choose.
Highest help used here: none
For Further Reading and Exploration
These are outside sites with their own rules. You will see a notice before you leave. Pick one, not all.
Automate the Boring Stuff with Python
Free book to read online. The functions chapter explains return values and what a function gives back.
Hands-on
May need an install
Ask an adult
CS50's Introduction to Programming with Python
Free Harvard course with videos and notes. The first lecture shows functions that give back a value you can use.
Hands-on
Advanced
May count visits
MIT OpenCourseWare 6.100L
Free college course notes and videos. It moves fast, so take one topic at a time. Look for the lectures on functions and what they return.
Hands-on
Advanced
May count visits
Raspberry Pi Foundation Projects
Step-by-step Python projects. Pick one that uses functions and watch what each one returns. Some need hardware, so check the parts list.