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Re: [pygame] Color, unpacking to r,g,b and r,g,b,a - ValueError: too many values to unpack



On Wed, Jun 17, 2009 at 4:29 PM, Lenard Lindstrom<len-l@xxxxxxxxx> wrote:
> René Dudfield wrote:
>>
>> Hi,
>>
>> one issue with the new Color type is unpacking to r,g,b or r,g,b,a.
>>
>> In some places Color is assumed to return (r,g,b) and others
>> (r,g,b,a), and now many things return a Color rather than a tuple.
>>
>> So I want to change Color to unpack to r,g,b,a or r,g,b.
>>
>> r,g,b = pygame.Color(1,2,3,4)
>> r,g,b,a = pygame.Color(1,2,3,4)
>>
>> Anyone have an idea how this can work?  Either in C or python?
>>
>> This is to keep backwards compatibility.
>>
>>
>> cheers,
>>
>
> Hi René,
>
> Are there cases where this is breaking code? For the most part I believe
> Pygame functions returned 4-tuples. So Color is just pretty much a drop-in
> replacement. If a program is using tuples to declare color values then the
> size is already known and unpacking is not a problem. It is
> Surface.get_palette and get_palette_at, which originally returned 3-tuples,
> where we run into problems. So here are the choices I see. One, just accept
> that the new get_palette and get_palette_at will break things, just as any
> program that tries to use a color return value as a dictionary key will now
> break. How many programs actually use color palettes anyway? Two, give Color
> a size property. If alpha is set None it becomes length 3. But then how does
> one represent this internally without adding another field to the Color C
> structure? Declare the color component values as C ints? Three, create a new
> Color subtype of length 3 having a fixed alpha of 255. I'm not happy with
> any of the choices but prefer three. Any other ideas?
>
> Lenard
>
>

hi,

yeah for example in solarwolf:
  File "solarwolf-1.5/code/gamemenu.py", line 70, in load_game_resources
    pal = [(g,g,b) for (r,g,b) in origpal]

  File "solarwolf-1.5/code/objshot.py", line 28, in load_game_resources
    for (r,g,b) in origpal]


hrmm.  I think a 3 element Color subtype might be the way to go.
Maybe we don't even need a subtype, but just a length property that
can be 1,2,3, or 4?  As you say get_palette(_at) could return len 3
Colors.

If it could unpack to 3, or 4 depending on the number of elements on
the left, I think I'd prefer that though.



cheers,