Tkinter.Canvas.create_line.coords

Bengt Richter bokr at oz.net
Sun Jun 1 10:37:02 CEST 2003


On Sun, 1 Jun 2003 09:53:20 +0200 (CEST), Arnd Baecker <arnd.baecker at web.de> wrote:

>Hi,
>
>I have a question concerning modifying a line created
>within a Canvas:
>
>It boils down to that (for `plot`  being a Canvas)
>    self.plot.coords(self.line,10,0,10,10,80,100,100,200)
>works, whereas
>    liste=[10,0,10,10,80,100,100,200]
>    self.plot.coords(self.line,liste)
I would try prefixing a '*' on the theory that the function is defined like foo below:
     self.plot.coords(self.line, *liste)

Notice:
 >>> def foo(first, *rest): print first,rest
 ...
 >>> foo(1,2,3,4)
 1 (2, 3, 4)
 >>> r = [2,3,4]
 >>> foo(1,r)
 1 ([2, 3, 4],)
Note what happened in the preceding: the entire r simply became the first and only
arg in the args tuple, which has length 1 instead of 3.

 >>> foo(1,*r)
 1 (2, 3, 4)
Compare this result to the original. We have unpacked r into the arg sequence,
so the r elements show up as if they had been passed as separate args.

>raises the error:
>    self.tk.splitlist(
>    TclError: bad screen distance "[10,"
>((Maybe the example below more clearly demonstrates what I mean here.))
>
>Actually, help(Tkinter.Canvas.coords) gives
>  coords(self, *args) unbound Tkinter.Canvas method
looks like foo above.

[...]

If the above works, we can go on to the next problem, which someone else
will have to get into if it's going to happen tonight ;-)

Regards,
Bengt Richter




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