python: option menu via TKinter not showing in my UI

Question

So i have simple application with 2 labels and 2 option_menu:

import sys

if sys.version_info[0] >= 3:
    import tkinter as tk
else:
    import Tkinter as tk


class App(tk.Frame):

    def __init__(self, master):
        tk.Frame.__init__(self, master)


    def update_options(self, *args):
        countries = self.dict[self.variable_a.get()]
        self.variable_b.set(countries[0])

        menu = self.optionmenu_b['menu']
        menu.delete(0, 'end')

        for country in countries:
            menu.add_command(label=country, command=lambda nation=country: self.variable_b.set(nation))


    def create_labels(self):
        tk.Label(root, text='').grid(row=0)
        tk.Label(root, text='Produtct:').grid(row=1, padx=10, pady=5)
        tk.Label(root, text='Application:').grid(row=2, padx=10, pady=5)

    def create_option_menu(self):
        self.dict = {
            'Mobile': ['ios', 'android'],
            'Test': ['1', '2', '3']
        }

        self.variable_a = tk.StringVar(self)
        self.variable_b = tk.StringVar(self)

        self.variable_a.trace('w', self.update_options)

        self.optionmenu_a = tk.OptionMenu(self, self.variable_a, *self.dict.keys()).grid(row=1, column=1, sticky="NSWE")
        self.optionmenu_b = tk.OptionMenu(self, self.variable_b, '').grid(row=1, column=1, sticky="NSWE")

        self.variable_a.set('Mobile')


if __name__ == "__main__":
    root = tk.Tk()
    app = App(root)
    app.create_labels()
    app.create_option_menu()
    app.mainloop()

And when I select some option from the first option menu the second option menu changed accordingly.

And i have problem that I cannot see my option menu and i cannot figure why. This is my exception:

Exception in Tkinter callback Traceback (most recent call last):
File "C:\Python37\lib\tkinter_init_.py", line 1705, in call return self.func(*args) File "C:/HW_Automation_Python/robot-framework/gui/init.py", line 19, in update_options menu = self.optionmenu_b['menu'] TypeError: 'NoneType' object is not subscriptable

See http://stackoverflow.com/q/1101750/7432 – Bryan Oakley Sep 25 '20 at 20:35 — Bryan Oakley, Sep 25 '20 at 20:35

score 1 · Accepted Answer · edited Nov 28 '20 at 11:38

Just change your respective part of code to this:

self.optionmenu_a = tk.OptionMenu(root, self.variable_a, *self.dict.keys())
self.optionmenu_a.grid(row=1, column=1, sticky="NSWE")
self.optionmenu_b = tk.OptionMenu(root, self.variable_b, '')
self.optionmenu_b.grid(row=2, column=1, sticky="NSWE")

Firstly, you are saying grid() on the same line as declaration which makes the variable have None as the value. Check here for more information on this.
Secondly, you forgot to specify a master option, like root for the widget.

python: option menu via TKinter not showing in my UI

1 Answers1