How to create a class to close GUI and exit Python - python-3.x

Question

I have been trying to find a way to do this for a while to no avail. I would like to create a class to completely close my GUI in tkinter and I'm not having much luck. I've tried sys.exit and .destroy() a few different ways. I can manage to do what I want without using classes but I'm rather new to OOP. Here is my code:
import sys as system
import tkinter as tk
from tkinter import ttk
class headerFrame(ttk.Frame):
def __init__(self, container):
super().__init__(container)
#setup the grid layout manager
self.columnconfigure(0, weight=1)
self._create_widgets()
def _create_widgets(self):
#header bar
canvas = tk.Canvas(self, bg='#0066cc', highlightthickness=0, height=45, width=600)
canvas.grid(column=0, row=0, sticky=tk.W)
label = ttk.Label(self, text='Production Assistant', background='#0066cc', foreground='White', font=('calibri', 18, 'bold'))
label.grid(row=0, column=0)
class loginFrame(ttk.Frame):
def __init__(self, container):
super().__init__(container)
#setup the grid layout manager
self.columnconfigure(0, weight =1)
self.columnconfigure(0, weight=3)
self._create_widgets()
def _create_widgets(self):
#username
ttk.Label(self, text='Username: ', justify='right').grid(row=0, column=0, sticky=tk.E)
username = ttk.Entry(self, width=33)
username.focus()
username.grid(row=0, column=1, sticky=tk.W)
#password
ttk.Label(self, text='Password: ', justify='right').grid(row=1, column=0, sticky=tk.E)
password = ttk.Entry(self, width=33, show='*')
password.grid(row=1, column=1, sticky=tk.W)
#add padding
for widget in self.winfo_children():
widget.grid(padx=0, pady=5)
class loginButtonFrame(ttk.Frame):
def __init__(self, container):
super().__init__(container)
#setup the grid layout manager
self.columnconfigure(0, minsize=62)
self._create_widgets()
def _create_widgets(self):
#buttons
ttk.Button(self, text='Login', width=15).grid(row=0, column=1)
ttk.Button(self, text='Forgot Login', width=15).grid(row=0, column=2)
ttk.Button(self, text='Request Access', width=15).grid(row=1, column=1)
ttk.Button(self, text='Exit', width=15, command=exitButton).grid(row=1, column=2)
#add padding to buttons
for widget in self.winfo_children():
widget.grid(padx=3, pady=3)
class exitButton():
def exit():
#code to close gui and program
#create the main application
class mainLogin(tk.Tk):
def __init__(self):
super().__init__()
self.title('Login')
self.geometry('325x175')
self.resizable(0, 0)
self.configure(background='#444444')
#windows only (remove the minimize/maximize buttons)
self.attributes('-toolwindow', True)
#TCL to center the screen
self.eval('tk::PlaceWindow . center')
#layout on the root window
self.columnconfigure(0, weight=1)
self._create_Styles()
self._create_widgets()
def _create_Styles(self):
#create styles
s = ttk.Style()
s.configure('TFrame', background='#444444')
s.configure('TLabel', background='#444444', foreground='white')
s.configure('TButton', background='#878683', foreground='black')
def _create_widgets(self):
#create the header frame
_header_frame = headerFrame(self)
_header_frame.grid(column=0, row=0)
#create the login frame
_login_frame = loginFrame(self)
_login_frame.grid(column=0, row=1, sticky=tk.N)
#create the button frame
_login_button_frame = loginButtonFrame(self)
_login_button_frame.grid(column=0, row=2)
if __name__ == '__main__':
app = mainLogin()
app.mainloop()
class exitButton() is what I would like to call from multiple different pages in the application to close everything.
Any help is appreciated, I'm trying to learn as I build so if you have any suggested reading based around Python that would help with this I would appreciate it!