optionmenu.py

from tkinter import *

class ListChanger:
    def __init__(self):
        self.root = Tk()
        self.quit = False ##used for quitting the application
        self.root.protocol("WM_DELETE_WINDOW", self.quitting) ##setting the [X] button to run code rather than tring to force quit the app
        self.list1 = ["1", "2", "3", "4"] ##some lists to use. this can be replaced by db queries insetad
        self.list2 = ["a", "b", "c", "d"]

    def list_changer(self, frame, option, lb): ##this will switch the lists around
        children = frame.winfo_children() ##gets all children of a widget
        for child in children: ## for all the children of the widget
            child.pack_forget() ##this only works if pack() is used rather than grid()
            child.destroy() ##destroys the widget from memory

        if option == "1": ##simple switch case
            lOPTIONS = self.list1
        elif option == "2":
            lOPTIONS = self.list2
        else:
            lOPTIONS = [None] #prevents any errors

        ##rebuiding the option menu with a new list
        lvariable = StringVar(frame)
        lvariable.set(lOPTIONS[0])
        ldrop = OptionMenu(*(frame, lvariable) + tuple(lOPTIONS))
        ldrop.pack(side=TOP)

        ##for listbox
        size = lb.size()
        for i in range(size):
            lb.delete(0)
        for i in range(len(lOPTIONS)): ##copyinh lOPTIONS form above but can be canged to any list
            lb.insert(i, lOPTIONS[i])

    def tracer(self, a, b, c, event, strvar, frame, lb): #a, b and c are auto generated from the trace() method and can be ignored but are required
        option = strvar.get() ##get what option is currently selected
        self.list_changer(frame, option, lb) ##run the changer with the option and the holder Frame

    def main(self):
        baseOptions = Frame(self.root)
        baseOptions.pack(side=TOP)
        bOPTIONS = ["1", "2"]
        bvariable = StringVar(baseOptions)
        bvariable.set(bOPTIONS[0])
        bdrop = OptionMenu(*(baseOptions, bvariable) + tuple(bOPTIONS))
        bdrop.pack(side=TOP)

        holderFrame = Frame(self.root) ##this frame should contain the list you want to change. Makes deleting the optionMenu easier
        holderFrame.pack(side=TOP)

        lOPTIONS = self.list1 ##creating the changeable list using the default options.
        lvariable = StringVar(holderFrame)
        lvariable.set(lOPTIONS[0])
        ldrop = OptionMenu(*(holderFrame, lvariable) + tuple(lOPTIONS))
        ldrop.pack(side=TOP)


        holderFrame2 = Frame(self.root)
        holderFrame2.pack(side=TOP)
        lb = Listbox(holderFrame2)
        lb.pack()
        for i in range(len(self.list1)):
            lb.insert(i, self.list1[i])

        #the trace() function can be used on any var,(strvar, intvar etc.) and is an event generated when that var is changed.
        bvariable.trace("w", lambda a, b, c, e=Event(), v=bvariable, f=holderFrame, l=lb: self.tracer(a, b, c, e, v, f, l))

        while not self.quit: ## helps closing the application
            self.root.update_idletasks() ##do not use root.mainloop() as it breaks other stuff such as sql, ftp and some web stuff by force closing the connection unsafly
            self.root.update()

    def quitting(self):
        self.quit = True

if __name__ == "__main__":
    try:
        app = ListChanger()
        app.main()
    except Exception as err:
        print("There was an Error")
        print(err)