How to access the selected variable in tkinter python

Question

I am trying to run queries by getting user inputs from drop downs. I have multiple drop downs and would like to change subsequent drop downs based on user selections. For example, if there are two drop downs state and city. If someone chooses a city, then there should be only one state in the state drop down and is someone selects a state, then only cities in that state should show up. I was trying to access the variable the user selects when he/she clicks on the drop down so that I can run specific queries and manipulate the queries. But I can only do it when the user clicks the confirm button and calls the function that has var.get().

conn = pyodbc.connect("{Connection String}")
cursor = conn.cursor()


cursor.execute('query to get states;')
states = cursor.fetcall()
state_list = []
for state in states:
    state_list.append(state[0])


def on_change_selection(value):
    state = selected_state.get()
    cursor.execute('select cities from XYZ where state = \'%s\'' %(state))
    cities = cursor.fetcall()
    city_list = []
    for city in cities:
        city_list.append(city[0])

    '''At this point I want the city_list to get updated in the already existing drop down option of cities'''

root = Tk()
selected_state = StringVar(value=state_list[0])
op_state = OptionMenu(root, selected_state, *(state_list), command=on_change_selection)
op_state.pack()
select_city = StringVar (value = city_list[0])
op_city = OptionMenu(root, selected_city, *(city_list), command=some_function())
op_city.pack()

The solution that I was thinking is just convoluted where within every function the Window gets updated with new option. I am sure there is a better way of doing this.

Also, if I want to use ComboBox and basically a lot of filters, do you suggest using PyQt5? I have never used GUIs before. Thank you in advance.

furas · Accepted Answer · 2016-12-15 19:55:56Z

2

OptionMenu has option command= similar to Button. It is used to execute function everytime you change selection in OptionMenu

import tkinter as tk

def on_change_selection(value):
    print('   value:', value)
    print('selected:', selected.get())

root = tk.Tk()

options = ["one", "two", "three"]

selected = tk.StringVar(value="one")

#selected = tk.StringVar()
#selected.set("one")

op = tk.OptionMenu(root, selected, *(options), command=on_change_selection)
op.pack()

root.mainloop()

answered Dec 15, 2016 at 19:55

furas

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2 Comments

Suraj Nagabhushana Ponnaganti Over a year ago

Another issue that I have been facing is that when the list becomes huge, OptionMenu does not help. I am trying to use ComboBox with a scroll bar. Does that have a similar command = feature? Thank you. This is exactly what I was looking for.

furas Over a year ago

you can use bind() to assign function to Combobox - simple example

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