from tkinter import *
from tkinter.ttk import *

window = Tk()

window.title("Welcome to Tkinter!")
window.geometry('400x300+30+200')

combo = Combobox(window)

#combo['values'] = ("a", "b", "c", "d", "Another character", 1001)

combovals = "Ankara Brno Dakkar Helsinki Oslo Perth Rome Seoul Vienna Warsaw"
combo['values']= tuple( combovals.split() )

combo.current(6) #set the selected item
combo.grid(column=0, row=0)

window.mainloop()