main() creates undefined error when running starter file

Question

I am going to be writing a program with this starter file provided to me by my instructor. The issue is is that the file she gave us does not run. I don't know if this is because I am using IDLE, or if the code only runs on certain operating systems.

For example, I use Windows, but my teacher uses both Windows and Linux systems. I cannot get a hold of her to figure out the issue, so I was hoping you guys could.

Currently, when I run the starter file, I get an error:

TypeError: main() is not defined.

When I switch main() for GUI() at the bottom of the program, I get a new error:

TypeError: __init__() missing 1 required positional argument: 'rootWindow'

This is the full code:

from tkinter import*
from tkinter import tk

class GUI:
    def __init__(self,rootWindow):
        self.label = ttk.Label(rootWindow, text="Hellow World!")
        self.label.grid(row=0,column=0)

        self.button1=ttk.Button(rootWindow,text="Hello",command=self.hello)
        self.button1.grid(row=0,column=1)
        self.button2=ttk.Button(rootWindow,text="Bye",command=self.bye)
        self.button2.grid(row=0,column=2)

    def bye(self):
        self.label.config(text="GoodbyeWorld!")

    def hello(self):
        self.label.config(text="HelloWorld!")

    def main():
        global label
        rootWindow = Tk()

        gui = GUI(rootWindow)
        rootWindow.mainloop()

main()

Answer 1

There are two problems with this code:

1. You need to unindent the main function, because otherwise you can't just call main because it is a part of the GUI class.

2. The imports are messed up. You need to import tkinter as ttk because otherwise ttk is undefined, and import Tk instead of import tk.

Note that I am using Python 3, so yours may be slightly different if you're using Python 2.

The full corrected code is below:

import tkinter as ttk
from tkinter import Tk

class GUI:
    def __init__(self,rootWindow):
        self.label = ttk.Label(rootWindow, text="Hellow World!")
        self.label.grid(row=0,column=0)

        self.button1=ttk.Button(rootWindow,text="Hello",command=self.hello)
        self.button1.grid(row=0,column=1)
        self.button2=ttk.Button(rootWindow,text="Bye",command=self.bye)
        self.button2.grid(row=0,column=2)

    def bye(self):
        self.label.config(text="GoodbyeWorld!")

    def hello(self):
        self.label.config(text="HelloWorld!")

def main():
    global label
    rootWindow = Tk()

    gui = GUI(rootWindow)
    rootWindow.mainloop()

main()