ttk_combobox_01.py

# =========================================================
# For ttk info: docs.python.org/3/library/tkinter.ttk.html
#
# Example from: stackoverflow.com/questions/17757451/
#               simple-ttk-combobox-demo
# =========================================================

import sys

if sys.version_info.major is 3:
    from tkinter import *
    from tkinter import ttk
    py3 = True
else:
    from Tkinter import *
    import ttk
    py3 = False

# ---------------------------------------------------------
#
# ---------------------------------------------------------

class App:

    def __init__(self, parent):
        self.parent = parent
        self.value_of_combo = 'X'
        self.combo()

    def newselection(self, event):
        self.value_of_combo = self.box.get()
        print(self.value_of_combo)

    def combo(self):
        self.box_value = StringVar()
        self.box = ttk.Combobox(self.parent, textvariable=self.box_value)
        self.box.bind("<<ComboboxSelected>>", self.newselection)
        self.box['values'] = ('X', 'Y', 'Z')
        self.box.current(0)
        self.box.grid(column=0, row=0)

# ---------------------------------------------------------
# --- main
# ---------------------------------------------------------

if __name__ == '__main__':
    root = Tk()
    app = App(root)
    root.mainloop()