title: Set a default value for a ttk Combobox
body: <p>I'm using Python 3.2.1 in Arch Linux x86_64. 
  This one is really driving me crazy: I just want to have a default, preselected value for a <code>ttk.Combobox</code> as soon as I grid it. This is my code:</p>
  
  <pre><code>from tkinter import Tk, StringVar, ttk
  
  root = Tk()
  
  def combo(parent):
      value = StringVar()
      box = ttk.Combobox(parent, textvariable=value, state='readonly')
      box['values'] = ('A', 'B', 'C')
      box.current(0)
      box.grid(column=0, row=0)
  
  combo(root)
  
  root.mainloop()
  </code></pre>
  
  <p>Which draws an empty <code>Combobox</code>. What's funny is that if I don't use a function it works perfectly:</p>
  
  <pre><code>from tkinter import Tk, StringVar, ttk
  
  root = Tk()
  
  value = StringVar()
  box = ttk.Combobox(root, textvariable=value, state='readonly')
  box['values'] = ('A', 'B', 'C')
  box.current(0)
  box.grid(column=0, row=0)
  
  root.mainloop()
  </code></pre>
  
  <p>Of course, in the real program I have to use a function, so I need another solution.</p>