Tkinter/scrollbar/canvas question

[Saul Spatz]

It works if you change it like so:

from tkinter import *
class ShowList(Frame):
        def __init__(self, root):
                Frame.__init__(self, root)
                self.grid()
                self.draw_widgets()
        def draw_widgets(self):
                cframe = Frame(self)
                cframe.grid(row=1, sticky=N+S+E+W)
                canv = Canvas(cframe)
                canv.grid(row=0, column=0, sticky=N+S+E+W)
                vscroll = Scrollbar(cframe, orient=VERTICAL, command=canv.yview)
                hscroll = Scrollbar(cframe, orient=HORIZONTAL, command=canv.xview)
                vscroll.grid(row=0, column=1, sticky=N+S)
                hscroll.grid(row=1, column=0, sticky=E+W)
                canv["xscrollcommand"] = hscroll.set
                canv["yscrollcommand"] = vscroll.set
                aframe = Frame(canv)
                id = canv.create_window(0,0,window=aframe, anchor=N+W)
                for i in range(0,100):
                        Label(aframe, text=str(i), anchor=N+W).grid(row=i, column=0)
                aframe.update_idletasks()
                canv["scrollregion"]=canv.bbox(ALL)
root  = Tk()
m=ShowList(root)
root.mainloop()

You have to call update_idletasks to force the canvas to be mapped to screen; until it is mapped, its bounding box is (0,0,1,1).  You can call update_idletasks through any widget.

That said, I wonder if it wouldn't be better to put canvas objects directly on the canvas, instead of putting widgets in a frame on the canvas.  The way you're doing it, you can't give the widgets tags, which are what give the canvas its real power.