[Pythonmac-SIG] Tkinter ttk question

[wrw at mac.com]

This may or may not be the best place to ask this, but here goes:

I'm exploring different GUI packages for python programs I'm writing.  I've played a bit with wx and now am exploring Tkinter and ttk 8.5 following the tutorial at http://www.tkdocs.com/tutorial.

The first example program is pasted in below:

#!/usr/bin/env python
from Tkinter import *
import ttk

def calculate(*args):
    try:
        value = float(feet.get())
        meters.set((0.3048 * value * 10000.0 + 0.5)/10000.0)
    except ValueError:
        pass
    
root = Tk()
root.title("Feet to Meters")

mainframe = ttk.Frame(root, padding="5 5 5 5")  # padding order: West, Top, East, South
mainframe.grid(column=0, row=0, sticky=(N, W, E, S))
mainframe.columnconfigure(0, weight=1)
mainframe.rowconfigure(0, weight=1)
feet = StringVar()
meters = StringVar()
feet_entry = ttk.Entry(mainframe, textvariable=feet, width=9)
feet_entry.grid(column=2, row=1, sticky=(W, E))
meters_entry = ttk.Entry(mainframe, textvariable=meters, width = 9)
meters_entry.grid(column = 2, row = 2, sticky =(W, E))
ttk.Button(mainframe, text="Calculate", command=calculate, default = "active").grid(column=3, row=3, sticky=W)
ttk.Label(mainframe, text="feet").grid(column=3, row=1, sticky=W)
ttk.Label(mainframe, text="is equivalent to").grid(column=1, row=2, sticky=E)
ttk.Label(mainframe, text="meters").grid(column=3, row=2, sticky=W)

for child in mainframe.winfo_children(): child.grid_configure(padx=5, pady=5)

feet_entry.focus()
root.bind('<Return>', calculate)

root.mainloop()


Quoting from the explanation:
Next, we create a frame widget, which will hold all the content of our user interface, and place that in our main window. The"columnconfigure"/"rowconfigure" bits just tell Tk that if the main window is resized, the frame should expand to take up the extra space.

The problem I'm having is that this doesn't work.  If I resize the window, the light gray background doesn't expand with the root window.  I get a light gray patch the size of the original frame, but it is surrounded by white space.  Can anyone tell me what I'm doing wrong.

64-bit Python 2.7 from python.org and I believe, but can't confirm, that Tkinter and ttk are from Active State.
Mac OS X 10.8.2, 2 x Quad processor Intel Xeon. 

As an additional query, is there another source for Tkinter and ttk?

Thanks in advance,
Bill
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