how can I create a menuBar using tkinter in python - python-3.x

Question

I really hope that you understand the following question, because I wasn't sure how to ask this question so I hope you can help me, if not let me now
I want to make a program to practise my python programming skill. I want to make a store program where an employee could input items with the price, and where he could sell the items. I want to make it that one “page” is the items input an another “page” is the sell page. To so that I want to make a menu bar where the employee could press on the let's say input button and go to input items page, but when he wants to sell items he presses on the sell button and then he goes to the sell page but only the screen changes, not that there comes another tab/window.
I really hope I explained my problem good enough
Thanks in advance!!

Answer 1

Based on your comments to the question, it appears your main problem is that you don't know how to make a menubar, so I will address that part of the question.
Every top level window (instances of Tk and Toplevel) have a menu attribute that can be set to an instance of a Menu object. This menu can itself have dropdown menus, and that combination is what makes a menubar.
In order to make this work you must first create the menu, and then associate that menu with the window.
import tkinter as tk
root = tk.Tk()
self.menubar = tk.Menu()
root.configure(menu=self.menubar)
To create the sub-menus you must do something very similar. First, create a new Menu instance, then associate it with the menubar using add_cascade. Typically, the menu will be a child of the menubar. You use the add_command method to add items to the sub-menu.
In your case, you might want to create a "View" menu with items for switching between "Input" and "Sell". It would look something like this:
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)
Example
Here is a complete working example. To keep it simple and on topic it doesn't actually switch pages. Instead, it just displays the "page" in a label.
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()