What are the alternatives to Globals in Python using Tkinter

Question

I am teaching a class and have been told to avoid global statements using Python and Tkinter. I don't want to teach Classes to my students yet

I know I can create all my entry boxes and labels out of a subroutine and my code will work, but this is just teaching a different bad practice

from tkinter import *

def print_name():
    print(entry_location.get())

def main():
    global main_window,entry_location
    main_window =Tk()
    Button(main_window, text="Print Name",command=print_name) .pack()
    entry_location = Entry(main_window)
    entry_location.pack()
    main_window.mainloop()

main()

This works with the global statement, but short of removing the code in main() from the subroutine is there an alternative?

Answer 1

In your example, you can eliminate globals by registering a lambda function to the button; this lambda function collects te value in the entry, and passes it as a parameter to print_name .

import tkinter as tk

def print_name(text=''):   # <- now receives a value as parameter
    print(text)

def main():
    main_window = tk.Tk()
    entry_location = tk.Entry(main_window)
    tk.Button(main_window, text="Print Name", command=lambda: print_name(entry_location.get())).pack()
    entry_location.pack()
    main_window.mainloop()

main()

Note:

This answers the special case of your example; it is not a generic answer to eliminating globals entirely. Alternative approaches could be to place the variables needed globally in a dictionary, or a list, thus permitting their modification in the local spaces, but in the end, it might become more complicated than using a proper class.
As suggested by @AndrasDeak, it is better to avoid star imports.

Answer 2

as phydeaux said, you can do this py simply passing the variables as parameters.

full ammended code shown below:

from tkinter import *

def print_name(entry_location):
    print(entry_location.get())

def main(main_window, entry_location):
    main_window =Tk()
    Button(main_window, text="Print Name",command=print_name) .pack()
    entry_location = Entry(main_window)
    entry_location.pack()
    main_window.mainloop()

main(main_window, entry_location)