动态更新选项菜单 tkinter

Question

I am trying to read.xlsx worksheets using tkinter. But code is posting error of "TypeError: 'NoneType' object is not subscribable". I have made enough trial on it but not able to understand the issue with the code.

import openpyxl
from tkinter import filedialog
from tkinter import *
    
class data:

    def __init__(self,master):

        self.master = master
        master.title("App")
        master.geometry("600x200")
        master.resizable(0,0)
        
        x,y = 30,20
        self.options = ['A',"B"]
        self.om_variable = StringVar()
        # self.om_variable.set(self.options[0])
        # self.om_variable.trace('w', self.option_select)
        self.om = OptionMenu(self.master, self.om_variable, *self.options).place(x = x+300,y = y+80)
        Brw_2   = Button(master = self.master, text = 'Browse', width = 6, command=self.update_option_menu).place(x = x+500,y = y+40)

    def update_option_menu(self):

        self.om_variable.set('')
        self.om["menu"].delete(0, "end")
        xyx = self.get_SheetsName(r"C:\_Code\Inputs\SomeExcelFile.xlsx")
        print("---->",xyx)
        for string in xyx:
            self.om["menu"].add_command(label=string, 
                             command=lambda value=string: self.om_variable.set(value))           

    def get_SheetsName(self, excel_file):
        wb = openpyxl.load_workbook(excel_file)
        SH_lst = wb.sheetnames
        Sh_names = [sh for sh in SH_lst if "AllTags" in sh]
        return Sh_names

root = Tk()
myGui = data(root)
root.mainloop()

Answer 1

This is a common mistake. When you wrote this:

self.om = OptionMenu(self.master, self.om_variable, *self.options).place(x = x+300,y = y+80)

Python created an optionmenu and then called the .place() method. The result of that which is None is saved to self.om . What you want is for the optionmenu to be created then stored in self.om then placed using .place()

So you basically python interpreted it like this:

temp_var = OptionMenu(self.master, self.om_variable, *self.options)
self.om = temp_var .place(x = x+300,y = y+80)
del temp_var

What you should have written is:

self.om = OptionMenu(self.master, self.om_variable, *self.options)
self.om.place(x = x+300,y = y+80)

Tip: never directly call grid / place / pack after calling the constructor without saving the object to a variable.