How to prevent Tkinter frame resize?

[phil_nospam_schmidt at yahoo.com]

I am trying to prevent a user from resizing a frame beyond its
"natural" size as given by winfo_reqwidth and winfo_reqheight, without
any success. Can anyone make any suggestions, based on my code below?

Thanks!

from Tkinter import *

class Table(Frame):
    def __init__(self, master,
                 rows=['row 1'], cols=['col 1'],
                 row_labels=True,
                 col_labels=True,
                 row_buttons=True,
                 col_buttons=True):
	Frame.__init__(self, master)
	self.rows = rows
	self.cols = cols
        self.row_labels = row_labels
        self.col_labels = col_labels
        self.row_buttons = row_buttons
        self.col_buttons = col_buttons
        self.col_width = 6
        self.draw()
        self.bind('<Configure>', self.changed)
    def changed(self, ev):
        w, h = self.winfo_reqwidth(), self.winfo_reqheight()
        cfg = {}
        if ev.height > h:
            cfg['height'] = h
        if ev.width > w:
            cfg['width'] = w
        if cfg:
            self.config(**cfg)   ######## this has no effect ########
    def draw(self):
        if self.row_labels or self.row_buttons:
            col = 1
            for t in self.cols:
                if self.row_labels:
                    e = Entry(self, width=self.col_width,
                              relief=GROOVE)
                    e.insert(INSERT, t)
                    e.grid(row=0, column=col+1)
                if self.row_buttons:
                    e = Label(self, text=col, width=self.col_width,
                              relief=GROOVE,bg='gray', fg='blue')
                    e.grid(row=1, column=col+1)
                col += 1
        if self.col_labels or self.col_buttons:
            row = 1
            for t in self.rows:
                if self.col_labels:
                    e = Entry(self, width=15,
                              relief=GROOVE)
                    e.insert(INSERT, t)
                    e.grid(row=row+1, column=0)
                if self.col_buttons:
                    e = Label(self, text=row, width=self.col_width,
                              relief=GROOVE,bg='gray', fg='blue')
                    e.grid(row=row+1, column=1)
                row += 1


if __name__ == '__main__':
    top = Tk()
    cols = ['col %s' % i for i in range(5)]
    rows = ['row %s' % i for i in range(5)]
    s = Table(top, rows=rows, cols=cols)
    s.pack(fill=BOTH, expand=1)
    mainloop()