Question

Just 5 days into Python, learning through Code Academy. I have no knowledge of any other language (very little knowledge of Ruby!).

What am I doing wrong with this code?

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Q: Write a function, by_three, that calls a second function, cube,
if a number is evenly divisible by 3 and "False" otherwise. You should
then return the result you get from cube. As for cube, that function
should return the cube of the number passed from by_three. (Cubing a
number is the same as raising it to the third power).

So, for example, by_three should take 9, determine it’s evenly
divisible by 3, and pass it to cube, who returns 729 (the result of
9**3). If by_three gets 4, however, it should return False and leave
it at that.

Lastly, call by_three on 11, 12, and 13 on three separate lines.

ANS:

def by_three(n):
    orig_num = n
    if (isinstance(orig_num, int) and orig_num%3 == 0 ):
        cube(orig_num)
    else:
        print "False"

def cube(orig_num):
    cube = orig_num**3
    print cube
    return

by_three(11)
by_three(12)
by_three(13)

When I run the above code, here is what I get. Why do these values appear in this way?

False
1728
False
==> None
False
False
1728
Oops, try again.

Answer 1

I can’t say why you’re seeing odd results. When I copy your code into the interpreter, I see:

>>> def by_three(n):
...     orig_num = n
...     if (isinstance(orig_num, int) and orig_num%3 == 0 ):
...         cube(orig_num)
...     else:
...         print "False"
... 
>>> def cube(orig_num):
...     cube = orig_num**3
...     print cube
...     return
... 
>>> by_three(11)
False
>>> by_three(12)
1728
>>> by_three(13)
False

I think this problem is a lot simpler than you’re making it, though. It’s hard to tell because the question is rather poorly written, but this would be my answer:

def by_three(n): return False if n % 3 else cube(n)

def cube(n): return n**3

by_three(11)
by_three(12)
by_three(13)

And this is what it looks like in the interpreter:

>>> def by_three(n): return False if n % 3 else cube(n)
... 
>>> def cube(n): return n**3
... 
>>> by_three(11)
False
>>> by_three(12)
1728
>>> by_three(13)
False