Tkinter: How to get frame in canvas window to expand to the size of the canvas?

Just for future reference in case anyone else needs to know:

        frame = Frame(self.bottom_frame)        frame.pack(side = LEFT, fill = BOTH, expand = True, padx = 10, pady = 10)        self.canvas = Canvas(frame, bg = 'pink')        self.canvas.pack(side = RIGHT, fill = BOTH, expand = True)        self.mailbox_frame = Frame(self.canvas, bg = 'purple')        self.canvas_frame = self.canvas.create_window((0,0),            window=self.mailbox_frame, anchor = NW)        #self.mailbox_frame.pack(side = LEFT, fill = BOTH, expand = True)        mail_scroll = Scrollbar(self.canvas, orient = "vertical",             command = self.canvas.yview)        mail_scroll.pack(side = RIGHT, fill = Y)        self.canvas.config(yscrollcommand = mail_scroll.set)        self.mailbox_frame.bind("<Configure>", self.OnFrameConfigure)        self.canvas.bind('<Configure>', self.FrameWidth)    def FrameWidth(self, event):        canvas_width = event.width        self.canvas.itemconfig(self.canvas_frame, width = canvas_width)    def OnFrameConfigure(self, event):        self.canvas.configure(scrollregion=self.canvas.bbox("all"))

Set a binding on the canvas <Configure> event, which fires whenever the canvas changes size. From the event object you can get the canvas width and height, and use that to resize the frame.