Converting a bidimensional list in a bidimensional array

[Scott David Daniels]

Santiago Romero wrote:
>...
  [I wrote]
>>        def __init__( self, bw, bh, tiles ):
>>          self.width, self.height = bw, bh
>>          self.tilemap = array.array('b', [0]) * bw * bh
>> Gives a pure linearization (you do the math for lines).
>  Do you mean : tilemap[(width*y)+x] ?
Yup, exactly.

...
>  What do you think about:
> - Memory Performance: Of course, my maps will take ( 16 bytes / 2-4
> bytes ) = 8 or 4 times less memory (32 / 64 bit processores) ...
> right?
How many distinct values do you have?  If you have under a hundred (and
they are all positive), the actual integers are shared, so a byte array
only saves you at 4:1 (or 8:1 on a 64-bit processor).

> - Speed Performance: Do you think that changing from list to Array()
> would improve speed? I'm going to do lots of tilemap[y][x] checks (I
> mean, player jumping around the screen, checking if it's falling over
> a non-zero tile, and so).
The Pythonic answer to this is, "try it both ways."  Don't intuit;
measure.  Now if you are as old-school as I am, you start by thinking,
"<invective expurgated>, I don't want to spend a week writing and
running benchmarks."

Joy, Python excels here.  at the command prompt (in 2.5, at least),
[a single line, I've broken it to three for newsgroup reading only]
      C:\> \python25\python -m -s "import array; a = [array.array('b',
                                         [0]*1000) for n in range(100)]"
                                  "v = a[1][2] + a[2][1] + a[3][3]"

You can also use:
     C:\> \python25\python -m -s "import m; m.setup()" "m.my_fun(123)"

Try it, you'll be addicted in no time.  Check the documentation on
package "timeit."

--Scott David Daniels
Scott.Daniels at Acm.Org