Python Tkinter can't select option in optionmenu

Question

I am having the problem where I am able to populate two optionmenus using Tkinter, (the second one dynamically based off the first), but I notice when I try to select one of the values in the second optionmenu, it does not allow me to select. I have noticed on the same GUI, sometimes when running another function, it will have this affect on a different option menu that worked fine prior to running the function. The options will show correctly, and the mouse can scan over them, but when you click on one it doesn't show that it has been selected, or execute the command set to it. Has anyone had this problem before?

Ok, so my hopes of someone else having the same issue are going down, and I'll include more code by request of some of the responders in case this might shed light on the issue. I'll try and pull everything applicable:

class GUI(Frame):

    def __init__(self, parent):
        Frame.__init__(self, parent)
        self.parent = parent
        self.build_gui()
    #reads the tabs on an excel and inputs the tab names as the values in the first optionmenu (this works)
    def read_board_tabs(self):
        #many of these variables in the function may not be defined. Ignore them as they are taken out of context. This should just help visually see the structure.
        filepath = 'Board Control.xlsx'
        wkbk = load_workbook((filepath))
        sheets = wkbk.get_sheet_names()
        print sheets
        return sheets

    #reads content of that excel tab chosen to populate the second optionmenu (populating the option menu works, but they can't be selected once populated)
    def read_serials(self, board):
        #many of these variables in the function may not be defined. Ignore them as they are taken out of context. This should just help visually see the structure.
        sheet = board
        if(sheet == ''):
            return ['']
        else:
            filepath = 'Board Control.xlsx'
            workbook = excel_transfer.workbook(filepath)
            wb = workbook.open_existing_workbook()
            ws = workbook.activate_specific_worksheet(wb, sheet)
            row = 1
            current_row = 0
            previous_row = 0
            serials = []
            #read the serials that exist for the board selected
            while current_row != None:
                previous_row = current_row
                row = row + 1
                cell = 'A' + str(row)
                current_row = workbook.read_new_cell(cell, ws)
                if(current_row != None):
                    serials.append(current_row)
            if(len(serials) == 0):
                serials = ['']
            self.BOARD_SERIAL_OPTION['menu'].delete(0, 'end')
            for item in serials:
                self.BOARD_SERIAL_OPTION['menu'].add_command(label=item)  

    #this is the command that won't execute when I try to select the second optionmenu value
    def find_board_info(self, serial):
        #many of these variables in the function may not be defined. Ignore them as they are taken out of context. This should just help visually see the structure.
        self.board_checkout_status_var.set('')
        sheet = (self.boards_var).get()
        new_search = StringFound.StringSearch(serial)
        results = new_search.read_board(sheet)
        if(results == ['']):
            self.boardstatusvar.set('No board was found')
        else:
            self.boardstatusvar.set('Board: %s Serial: %s' %(results[1], serial))
            self.boardstatus_locationvar.set('Found in file: %s' %results[0])
            self.boards_var.set('%s serial %s' %(results[1], serial))
            self.dispositionvar.set(results[3])            
            self.TXvar.set(results[5])  
            self.RXvar.set(results[6])   
            self.lastvar.set(results[10])  
            self.datevar.set(results[9])
            if(results[14] != None):
                self.currentvar.set(results[10]) 
            self.locationvar.set(results[4])     
            self.imagevar.set(results[8]) 
            self.notesvar.set(results[12]) 
        self.current_board_chosen = [sheet, serial, results[15]]

    #creates the gui
    def build_gui(self):
        n = Notebook(self)
        board_process = Tkinter.LabelFrame(self, text="Board Updates")
        n.add(board_process, text='Board Signout')
        n.pack()
        self.boards_var = StringVar()
        self.boards_var.set("")
        self.serials_var = StringVar()
        self.serials_var.set("")
        self.SEARCHBOARDFRAME = Tkinter.LabelFrame(board_process, text='Find Board')
        self.SEARCHBOARDFRAME.grid(row=0, column=0, sticky='WE')
        self.BOARD_SEARCH_LABEL = Label(self.SEARCHBOARDFRAME, text='Type:')
        self.BOARD_SEARCH_LABEL.grid(row=0, column=0, sticky='W', padx=5, pady=2)
        self.BOARD_SEARCH_OPTION = OptionMenu(self.SEARCHBOARDFRAME, self.boards_var, *self.list_of_boards, command=self.read_serials) 
        self.BOARD_SEARCH_OPTION.grid(row=0, column=1, sticky='W', padx=5, pady=2)   
        self.BOARD_SERIAL_LABEL = Label(self.SEARCHBOARDFRAME, text='Serial:')
        self.BOARD_SERIAL_LABEL.grid(row=1, column=0, sticky='W', padx=5, pady=2)
        self.BOARD_SERIAL_OPTION = OptionMenu(self.SEARCHBOARDFRAME, self.serials_var, *self.list_of_serials, command=self.find_board_info)
        self.BOARD_SERIAL_OPTION.grid(row=1, column=1, sticky='W', padx=5, pady=2)

if __name__ == '__main__':
    root = Tk()
    app = GUI(root)
    root.mainloop()

Answer 1

The problem is in these lines of code:

for item in serials:
    self.BOARD_SERIAL_OPTION['menu'].add_command(label=item)  

You are putting items in the option menu with a label, but you aren't giving them a command. The whole reason the Optionmenu widget exists is to add a special command to each item that gives the option menu its behavior. Unless you add that command when you dynamically create new items, those items won't do anything when you select them -- it's just a dumb menu with labels on it.

Unfortunately, the command that is associated with each item is returned from a private factory class (Tkinter._setit), so you don't have any officially supported way to add new items to an option menu. If you aren't afraid to use private commands, you can change your code to be this:

for item in serials:
    command=Tkinter._setit(self.serials_var, item, self.find_board_info)
    self.BOARD_SERIAL_OPTION['menu'].add_command(label=item, command=command)

For another way to solve this problem see Change OptionMenu based on what is selected in another OptionMenu