I'm developing an easy program and I need to get the value from a Combobox. It is easy when the Combobox is in the first created window but for example if I have two windows and the Combobox is in the second, I am not able read the value from that.

For example :

from tkinter import *
from tkinter import ttkdef comando():print(box_value.get())parent = Tk() #first created window
ciao=Tk()     #second created window
box_value=StringVar()
coltbox = ttk.Combobox(ciao, textvariable=box_value, state='readonly')
coltbox["values"] = ["prova","ciao","come","stai"]
coltbox.current(0)
coltbox.grid(row=0)
Button(ciao,text="Salva", command=comando, width=20).grid(row=1)
mainloop()

If I change the parent of the widget from ciao to parent it works! Can anyone explain me?

You cannot have two Tk() windows. one must be Toplevel.

To get the variable you can do box_value.get()

Example of a drop down box :

class TableDropDown(ttk.Combobox):def __init__(self, parent):self.current_table = tk.StringVar() # create variable for tablettk.Combobox.__init__(self, parent)#  init widgetself.config(textvariable = self.current_table, state = "readonly", values = ["Customers", "Pets", "Invoices", "Prices"])self.current(0) # index of values for current tableself.place(x = 50, y = 50, anchor = "w") # place drop down box print(self.current_table.get())