First Tkinter application. Comments please?

[Gerrit Holl]

Hello,

I just created my first Tkinter.Canvas application. Can someone please
be kind enough to comment on the code? Maybe my ``problem'' could be solved
much easier...

# cut here

from Tkinter import *

UP = 98      # keycodes
LEFT = 100
RIGHT = 102
DOWN = 104

class App:
    id = 0
    def __init__(self, root):
        self.root = root

        self.draw = Canvas(self.root, width=400, height=400)
        self.draw.create_oval(0, 0, 10, 10, tags="it", fill="blue")
        self.draw.pack()
        
        # What's better: this, or binding <KeyPress> and ignoring everything
        # that's not a keycode of one of these?
        self.root.bind("<KeyPress-Up>", self.move_it)
        self.root.bind("<KeyPress-Down>", self.move_it)
        self.root.bind("<KeyPress-Left>", self.move_it)
        self.root.bind("<KeyPress-Right>", self.move_it)
        self.root.mainloop()

    def move_it(self, *args):
        # Because bind gives an argument, which I will always need, but
        # after doesn't give the argument.
        if len(args):
            self.dir = args[0] 

        if self.dir.keycode == UP:
            self.draw.move("it", 0, -1)
        elif self.dir.keycode == DOWN:
            self.draw.move("it", 0, 1)
        elif self.dir.keycode == RIGHT:
            self.draw.move("it", 1, 0)
        elif self.dir.keycode == LEFT:
            self.draw.move("it", -1, 0)

        # Because otherwise, it gets called twice as many times.
        if self.id:
            self.root.after_cancel(self.id)

        self.id = self.root.after(10, self.move_it)

App(Tk())
# cut here

If the code is ``good'' (I don't think it is), it might suit well for an
example in the Demo/tkinter/ dir. It costed me very much time to find out
how I had do do the after_cancel. I looked in the source, saw the
method and thought "what is the argument? "it"? "move_it"?". I ended up
looking in the source of idle.
I think that if this example is OK, it's a good example of using keycodes
and preventing the 'self.root.after(...)' to be executed too much.

regards,
Gerrit `who loves Tkinter now he finally understands it'.

-- 
"The IETF motto is 'rough consensus and running code'"
  
  -- Scott Bradner (Open Sources, 1999 O'Reilly and Associates)
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