title: Tkinter combobox - gracefully lose focus when click out of widget
body: <p>I have a ComboBox written in Python Tkinter that makes the horrible system alert sound when you click off of it without selecting something.</p>
  <p>For instance, when you hit the dropdown and select your item, it works fine. But if you hit the drop-down and then decide to click off, it will lose focus as expected, but it makes an alert sound. Can this be disabled in some way so it can gracefully lose focus without complaining? I'm on OSX 10.9 btw</p>
  <p>UPDATE -
  Minimally working code that produces the alert.</p>
  <pre><code>from Tkconstants import *
  import ttk
  import Tkinter
  
  class PyPrecursor():
  
      def __init__(self,root):
          self.root = root
          self.TabNotebook()
  
      def TabNotebook(self):
          self.main_notebook_frame = ttk.Notebook(self.root, name='main_notebook')
          self.main_notebook_frame.enable_traversal()
          self.OptionsF = ttk.Frame(self.main_notebook_frame, name='options')
          self.length_options_frame = ttk.LabelFrame(
          self.OptionsF, labelwidget=ttk.Label(font=('Arial', 15), text=&quot;Length Options:&quot;))
          self.hcdr3_length_label = ttk.Label(self.length_options_frame, text=&quot;HCDR3 Length&quot;)
          self.HCDR3_Length = Tkinter.StringVar()
          self.hcdr3_length_combo = ttk.Combobox(
          self.length_options_frame, values=[i for i in xrange(16, 36)], 
               textvariable=self.HCDR3_Length)
          self.hcdr3_length_combo.current(0)
          self.length_options_frame.pack(side=TOP,fill=X,pady=5)
          self.hcdr3_length_label.pack(side=LEFT)
          self.hcdr3_length_combo.pack(side=LEFT,anchor=W)
          self.main_notebook_frame.pack(side=TOP,expand=1,fill=BOTH,padx=10,pady=10)
          self.main_notebook_frame.add(
              self.OptionsF, text=&quot;Input Options&quot;, underline=0, padding=2)
          self.main_notebook_frame.bind(&quot;&lt;&lt;NotebookTabChanged&gt;&gt;&quot;,self.update_)
  
      def update_(self,event):
          self.root.update()
  
  def main():
      root = Tkinter.Tk()
      PyPrecursor(root)
      root.mainloop()
      root.update_idletasks()
  
  
  if __name__ == '__main__':
      main()
  </code></pre>