Traversing through variable-sized lists

[Andrej Mitrovic]

On Feb 17, 11:56 pm, Dave Angel <da... at ieee.org> wrote:
> Andrej Mitrovic wrote:
> > On Feb 17, 8:24 pm, John Posner <jjpos... at optimum.net> wrote:
>
> >> On 2/17/2010 1:10 PM, Andrej Mitrovic wrote:
>
> >> <snip>
>
> > However the values list might have an uneven number of items. I would
> > like to make it as evenly distributed as possible, e.g.:
>
> > values =-2, -1, 0]
> > frames =obj1, obj2, obj3, obj4, obj5, obj6, obj7, obj8]
>
> > frames[0].func(values[0])  # func.(values[-2])
> > frames[1].func(values[0])  # func.(values[-2])
> > frames[2].func(values[1])  # func.(values[-2])
> > frames[3].func(values[1])  # func.(values[-1])
> > frames[4].func(values[1])  # func.(values[-1])
> > frames[5].func(values[2])  # func.(values[-1])
> > frames[6].func(values[2])  # func.(values[0])
> > frames[7].func(values[2])  # func.(values[0])
>
> > I'll be even more specific. I have a Minimum and Maximum value that
> > the user enters. The frame.func() function is a "translate" function,
> > it basically moves a frame in the application in one direction or
> > another depending on the argument value. So frame[0].func(2) would
> > move the frame[0] 2 pixels to the right. So what I want is the
> > function to create a smooth transition of all the frames from the
> > Minimum to the Maximum value. If minimum was 0, and maximum was 10,
> > I'd want the first frame moved 0 pixels (it stays in place), the last
> > frame to move 10 pixels, and the frames between are gradually moved
> > from 1 pixels to 9 pixels relative from their positions.
>
> > Perhaps I'm just overcomplicating. I'll have a look at some drawing
> > apps and see how they've implemented drawing straight lines under an
> > angle, I guess that could be called a gradual change of values.
>
> > Thanks for all the suggestions everyone, I'll have a look at the rest
> > shortly.
>
> I think you're overcomplicating.  If you have 27 frames, and you want
> frame 0 to move 0 pixels, and frame 27 to move 10 pixels, then you want
> to move frame[i] by i*10/27.  And since you do the multiply first, the
> fact that Python 2.x division gives you integers isn't a problem.
>
> There are fancier methods for drawing lines (bresenham for example), but
> the main purpose of them is to to avoid multiply and divide, as well as
> floats.  But in Python, an integer multiply is just as fast as an add or
> subtract, so there's no point.
>
> DaveA

Doh! Such a simple solution, just what I was looking for. Thanks!