title: Enable/Disable multiple Entry widgets using tkinter.grid()
body: <p>I'm coding a menu for a python minesweeper game that will allow players to enter in custom row, column and mine counts. I want to make it so that clicking the easy, medium, or hard radio buttons will disable all three entry widgets, and clicking the custom radiobutton will enable all three.</p>
  
  <p>My code:</p>
  
  <pre><code>from tkinter import *
  
  def customDisable():
      E_row.configure(state='disabled')
      E_row.update()
      E_col.configure(state='disabled')
      E_col.update()
      E_mine.configure(state='disabled')
      E_mine.update()
  
  def customEnable():
      E_row.configure(state='normal')
      E_row.update()
      E_col.configure(state='normal')
      E_col.update()
      E_mine.configure(state='normal')
      E_mine.update()
  
  menu=Tk()
  menu.title('Pysweeper V 1.0')
  ms=Canvas(menu,width=5,height=5)
  ms.data={}
  menu.resizable(0,0)
  
  T_row=Label(menu,text='Rows:',anchor=E).grid(row=1,column=2)
  T_col=Label(menu,text='Columns:',anchor=E).grid(row=2,column=2)
  T_mine=Label(menu,text='Mines:',anchor=E).grid(row=3,column=2)
  
  E_row=Entry(menu,state='normal').grid(row=1,column=3)
  E_col=Entry(menu,state='normal').grid(row=2,column=3)
  E_mine=Entry(menu,state='normal').grid(row=3,column=3)
  
  dif=IntVar()
  RB_easy=Radiobutton(menu, text='Easy',anchor=W,variable=dif,value=1,command=customDisable).grid(row=1,column=1,rowspan=2)
  RB_med=Radiobutton(menu, text='Medium',anchor=W,variable=dif,value=2,command=customDisable).grid(row=3,column=1,rowspan=2)
  RB_hard=Radiobutton(menu, text='Hard',anchor=W,variable=dif,value=3,command=customDisable).grid(row=5,column=1,rowspan=2)
  RB_cust=Radiobutton(menu, text='Custom game',variable=dif,value=4,command=customEnable).grid(row=7,column=1)
  </code></pre>
  
  <p>Executing the code gives me the following window with no errors: <a href="http://i.imgur.com/aNItO0f.png" rel="nofollow">http://i.imgur.com/aNItO0f.png</a></p>
  
  <p>However, when I select a radio button, the console prints an error:</p>
  
  <pre><code>Exception in Tkinter callback
  Traceback (most recent call last):
    File "C:\Python33\lib\tkinter\__init__.py", line 1442, in __call__
      return self.func(*args)
    File "C:\Python33\Minesweeper.py", line 212, in customDisable
      E_row.configure(state='disabled')
  NameError: global name 'E_row' is not defined
  </code></pre>
  
  <p>It appears that this error is caused by not passing in the E_row values, but I've gotten the method to work using .pack() instead of grid. Normally I'd just switch to .pack(); however, since the rest of my game is .grid() instead of .pack() I'm stuck using .grid for the menu as well. What am I missing here?</p>