Weird Loop Behaviour

[MRAB]

On 20/01/2012 20:47, Yigit Turgut wrote:
> Hi,
>
> In the following code, I am trying to run "black" screen for 3 seconds
> and respectively 2 seconds "white" screen. Black routine takes 3
> seconds and white 2 seconds, 2 x black + white = 8 seconds which
> should be the expected value but when I run it I get black-white-black-
> white   instead of black-white-black. Couldn't figure out what is
> wrong thus sharing the code as well ;
>
> white = False
>     while(end<8.00):
>         end = time.time() - start
>         if white:
>             screen.fill((255, 255, 255))
>             time.sleep(2)
>         else:
>             screen.fill((0, 0, 0))
>             time.sleep(3)
>         white = not white
>         pygame.display.update()
>     pygame.quit()

Could it be because you're setting 'end' after testing it?

It might be simpler as:

       while time.time() - start < 8:

Also, should it really be sleeping before updating the display? I
would've thought that it should be sleeping _after_ updating the
display.