python - Why does tkinter.ttk Combobox clear displayed value on initial selection only? -


i building gui in tkinter , seeing curious behaviour ttk.combobox. initializes fine, when select item dropdown, combobox display clears. happens first time make selection. start app > make selection > display clears > make selection > diplays normal. here's code (only pertinent parts brevity). combobox class fetches column database list , assigns values. otherwise, pretty straighforward tkinter.

import tkinter tk tkinter import messagebox tkinter import ttk tkinter import n, s, e, w tkinter import end, center  import dbmanager   class maingui(tk.tk):      """main gui class engcalc."""      def __init__(self, db_mngr):         """see class docstring."""         self.db = db_mngr         tk.tk.__init__(self)         tk.tk.wm_title(self, 'engcalc')         self.init_root_frame(master=self)      def init_root_frame(self, master=none):         """create , initialize main gui container."""         self.root_frame = ttk.frame(master)         self.root_frame.grid()          dbcombo(master=self.root_frame, controller=self,                 table='[materials(si)]', col='material')   class dbcombo(ttk.combobox):      """a dropdown combobox given column in database table."""      def __init__(self, master=none, controller=none,                  table=none, col=none, row=0, column=0):         """see class docstring."""         self.values = controller.db.fetch_list(table, col)         self.combovar = tk.stringvar()         ttk.combobox.__init__(self, master, values=self.values,                               textvariable=self.combovar)         self.current(0)         self.bind("<<comboboxselected>>", self.newselection)         self.grid(column=column, row=row)         self.state(['!disabled', 'readonly'])      def newselection(self, event):         """get value of combobox."""         self.combovar = self.get()         print(self.combovar)   if __name__ == '__main__':     db = '../db/test1.sqlite'     database = dbmanager.databasemanager(db)     foo = maingui(database)     foo.mainloop()

at 1 point in code self.combovar points instance of stringvar, later redefine self.combovar string. solution not redefine self.combovar inside newselection


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