title: Python tkinter: issues resizing frames
body: <p>I'm trying to resize a window in my GUI but one of my frames is getting left out and I'm not sure why. The window resizes fine horizontally, but when I try to resize vertically the frame with the button disappears. This is my first GUI so I'm sure there is something I'm missing...</p>
  
  <pre><code>from Tkinter import *
  from ttk import *
  
  class GUI(Frame):
      def __init__(self, root):
          Frame.__init__(self, root)
  
          self.root = root
  
          lbFrame = Frame(self.root)
          nbFrame = Frame(self.root)
  
          self.note = Notebook(nbFrame)
          self.note.pack(fill=BOTH, expand=YES)
  
          lbFrame.pack(side=LEFT, fill=BOTH, expand=YES)
          nbFrame.pack(side=RIGHT, fill=BOTH, expand=YES)
  
          self.make_file_viewer()
  
          # Label
          lblabel = Label(lbFrame, text='Files', background='#E8E8E8')
          lblabel.pack(side=TOP, expand=YES, padx=10, pady=10)
  
          # Listbox
          self.lb = Listbox(lbFrame, height=49, borderwidth=0, font=('Purisa', 11), selectmode=EXTENDED)
          self.lb.pack(side=BOTTOM, expand=YES, padx=10, pady=10)
  
      def make_file_viewer(self):
          fvwr = Frame(self.note)
  
          dataFrm = Frame(fvwr)
          btnFrm = Frame(fvwr)
          dataFrm.pack(side=TOP, fill=BOTH, expand=YES)
          btnFrm.pack(side=BOTTOM, fill=BOTH, expand=YES)
  
          fvwr.config(borderwidth=2)
          self.note.add(fvwr, text='File View')
  
          # Label
          self.lbl_fvwr_search = Label(dataFrm, text='Search Hits\t0', justify=LEFT)
          self.lbl_fvwr_search.pack(side=TOP, anchor=W, expand=YES)
  
          # Scrollbar
          scrollbar_fvwr = Scrollbar(dataFrm)
          scrollbar_fvwr.pack(side=RIGHT, fill=Y, expand=YES)
  
          # Textbox
          self.outputPanel_fvwr_text = Text(dataFrm, wrap='word', height=40, width=115, yscrollcommand=scrollbar_fvwr.set)
          self.outputPanel_fvwr_text.pack(side=LEFT, fill=BOTH, expand=YES)
          scrollbar_fvwr.config(command=self.outputPanel_fvwr_text.yview)
  
          # Start button
          viewBtn = Button(btnFrm, text='Start', width=8)
          viewBtn.pack(anchor=W, expand=YES)
  
  if __name__ == '__main__':
      root = Tk()
      app = GUI(root)
      root.mainloop()
  </code></pre>