Functions That Return Answers

You met functions in Phase I — you taught the turtle a trick with def and called it. Those functions did something (drew a shape). Today’s functions answer something: they compute a value and hand it back with return, so you can use the answer however you like. This is how programmers package up useful logic — and how you’ll transform data in Phase III.

return: hand back an answer

A function can return a value. Whatever you return becomes the result of calling it:

 
  

add(2, 3) runs the function, which returns 5. We store that in answer and print it. The function gave us a value to use.


Try it 🎯


    

  1. Write a multiply(a, b) function and use it to print 6 × 7.
    2. 

  2. Call add inside a print: print(add(10, 20)).
    3. 



return is not the same as print


This catches people. print shows a value on screen; return hands it back so the rest of your program can use it. Compare:


   
   
 
 
  

Because double_and_return hands back a value, we can do math with it (x + 1). A function that only prints can’t be used that way.


Combining returned values


The real power: use one function’s answer inside another expression:


   
   
 
 
  

You wrote the “how to compute an area” logic once, then reused it and combined the results.


A function that decides


A function can contain if and return different answers:


   
   
 
 
  

Predict it 🔮


What does this print? Notice the function uses return, and we print the result:


   
   
 
 
  

(25 — square(4) is 16, square(3) is 9, and 16 + 9 = 25. Because each call returns a number, we can add them.)


Fix the bug 🐞


This triple function is supposed to return three times its input, but the result comes out as None. It’s missing one keyword:


   
   
 
 
  

(The function computes n * 3 but never hands it back, so it returns nothing (None). Add return: return n * 3.)


Your mission 🚀


Write a function is_even(n) that returns True if a number is even and False if it’s odd. (Hint: a number is even when n % 2 == 0.) Then test it on a few numbers:


   
   
 
 
  

What you learned today


    

  • return hands a value back from a function so you can use it.
    • 

  • return is different from print — one gives back a value, the other just shows it.
    • 

  • You can combine returned values in bigger expressions, and return different things from inside if.
    • 

  • Functions let you write logic once and reuse it everywhere — the building block of bigger programs.
    • 



Next time is a project: a chatbot that reads what you type and replies, using everything from this phase. 🤖
   
 
 
 
Comments