tk_menu.py

import tkinter as tk


class MenuExample:

	def __init__(self):
		self.root = tk.Tk()
		self.label = tk.Label(self.root, width=25)
		self.label.pack(side="top", fill="both", expand=True, padx=20, pady=20)
		self._create_menubar()

	def _create_menubar(self):
		# create the menubar
		self.menubar = tk.Menu(self.root)
		self.root.configure(menu=self.menubar)

		# File menu
		fileMenu = tk.Menu(self.menubar)
		self.menubar.add_cascade(label="File", menu=fileMenu)
		fileMenu.add_command(label="Exit", command=self.root.destroy)

		# View menu
		viewMenu = tk.Menu(self.menubar)
		self.menubar.add_cascade(label="View", menu=viewMenu)
		viewMenu.add_command(label="Input", command=self.switch_to_input)
		viewMenu.add_command(label="Sell", command=self.switch_to_sell)

	def switch_to_input(self):
		# put the code to switch to the input page here...
		self.label.configure(text="you clicked on View->Input")

	def switch_to_sell(self):
		# put the code to switch to the sell page here...
		self.label.configure(text="you clicked on View->Sell")


app = MenuExample()
tk.mainloop()