Tkinter combobox - gracefully lose focus when click out of widget

Question

I have a ComboBox written in Python Tkinter that makes the horrible system alert sound when you click off of it without selecting something.

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

UPDATE - Minimally working code that produces the alert.

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="Length Options:"))
        self.hcdr3_length_label = ttk.Label(self.length_options_frame, text="HCDR3 Length")
        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="Input Options", underline=0, padding=2)
        self.main_notebook_frame.bind("<<NotebookTabChanged>>",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()

Answer 1

You might want to try this: self.hcdr3_length_combo.bell(displayof=1)

Not sure if it should be 1 or 0 though... If it doesn't work, maybe a containing widget throws the sound. Might want to apply it to the parent widget as well. I'm not familiar with python 2.7 and it doesn't throw a sound when I use python3 with slight modifications.

Usually when you can't find an option for a specific widget, you can find something in the general widget options. Just search "tkinter widget options" and you'll get some place like: https://effbot.org/tkinterbook/widget.htm