[Tutor] Fw: Traceback

[niyana morgan]

Okay yeah this helping.
I believe getNumber does actually return a number.
On Nov 18, 2014 7:29 PM, "Danny Yoo" <dyoo at hashcollision.org> wrote:

> On Tue, Nov 18, 2014 at 1:46 PM,  <niyanaxx95 at gmail.com> wrote:
> > I get this message:
> > Traceback (most recent call last):
> >   File "C:\Program Files (x86)\Wing IDE 101
> > 5.0\src\debug\tserver\_sandbox.py", line 87, in <module>
> >   File "C:\Program Files (x86)\Wing IDE 101
> > 5.0\src\debug\tserver\_sandbox.py", line 20, in main
> >   File "C:\Program Files (x86)\Wing IDE 101
> > 5.0\src\debug\tserver\_sandbox.py", line 70, in tilesForSize
> > builtins.TypeError: unsupported operand type(s) for -: 'NoneType' and
> 'int'
>
> Hi Niyana,
>
> Ok, let's look at the error message a bit more closely.  It's saying:
> "somewhere in tilesForSize, you're asking me to subtract a value
> that's not an int."
>
> Let's look at the definition of tilesForSize:
>
> ######################################
> def tilesForSize(size) :
>     pairs = int((size - tileSize) // int(2 * tileSize))
>     num = int(1 + (2 * pairs))
>     return num
> ######################################
>
> There is only a single place where subtraction is happening here, so
> we can point a finger at the sub-expression:
>
>     size - tileSize
>
>
> Assuming we can trust the error message, all we need to do now is
> figure out why:
>
>     size - tileSize
>
> is erroneous in this context.  size is one of the parameters, and
> tileSize is... I don't know what it is yet.  Global variable, perhaps?
>
> Let's assume, for the moment, that the problem is the parameter.  (If
> we guessed wrong, we'll double back and start looking at tileSize.)
>
>
> You may have heard the term: "Garbage in, garbage out".  Our job now
> is to look at how we got that input value, and at what point it was
> garbage.
>
>
> So at this point, I'd look at one of the call points of tilesForSize.
> The stack trace we're looking at says that it saw a problem when
> main() was calling tilesForSize, on line 20.  What does that line say?
>  It's one of these lines:
>
>     numCols = tilesForSize(roomWidth)
>     numRows = tilesForSize(roomLength)
>
> The source of the argument here is roomWidth and roomLength.  Where do
> those values come from?  Reading...  ah, they come from here:
>
>     roomWidth = getNumber(100, 500, "Enter a room width between 100
> and 500: ", "")
>     roomLength = getNumber(100, 450, "Enter a room length between 100
> and 450: ", "")
>
>
> Ok, so here's a question: does getNumber actually return a number?
> Have you tested this?
>
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