John Ladasky wrote:
> Hi, folks,
>
> Some of you may remember that I am teaching some high school students how
> to program. Because they all love graphics, I have been investigating the
> turtle module, which I gather is built on top of Tk. I can see that
> real-time applications are possible. I'm writing a classic
> "bouncing-balls" program to demonstrate to my students.
>
> In the main program code, I instantiate a turtle.Screen, named sc.
>
> I draw a bounding box, whose size is described by the variables edgew and
> edgeh. I have a list of Turtle objects, which I named balls. I have a
> timer interval stored in tick.
>
> In the main loop of my program, I bind a function to update the positions
> of the balls to a timer, thus:
>
> sc.ontimer(move_balls, tick)
>
> Inside my move_balls function, I could not get ANYTHING done without the
> following declaration:
>
> global balls, edgew, edgeh, tick
That's not limited to turtle, Python in general forces you to make shared
state explicit.
Simple alternatives to global would be a degenerate class
class state:
pass
or a magic import
import __main__ as state
With both of these (pseudo-)globals can be set with
state.some_global = some_value
However, most of the names you list above look like their values need not be
altered from within the function and thus the name not be declared global
anyway. To be sure you'd have to show us the code...
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