How do I create a popup window in tkinter?

Question

I have a problem creating a popup window for a program.

Code:

from tkinter import *
from tkinter import ttk
import tkinter as tk

def popupBonus():
    popupBonusWindow = tk.Tk()
    popupBonusWindow.wm_title("Window")
    labelBonus = Label(popupBonusWindow, text="Input")
    labelBonus.grid(row=0, column=0)
    B1 = ttk.Button(popupBonusWindow, text="Okay", command=popupBonusWindow.destroy())
    B1.pack()

class Application(ttk.Frame):
    def __init__(self, master):
        ttk.Frame.__init__(self, master)
        mainwindow = ttk.Frame(self)

        self.buttonBonus = ttk.Button(self, text="Bonuses", command=popupBonus)
        self.buttonBonus.pack()

The code generates a window with a button and when you press the button, it's supposed to generate a popup window with title "Window", text "Input", and have a button saying "Okay" to exit popup window and return to main window. However, I am getting this error.

 Traceback (most recent call last):
  File "D:\Softwares\Python 3.6.0\lib\tkinter\__init__.py", line 1699, in __call__
return self.func(*args)
  File "C:\Users\J---- M--\Desktop\Python\GUI-Messagebox 5.py", line 12, in popupBonus
B1 = ttk.Button(popupBonusWindow, text="Okay", command=popupBonusWindow.destroy())
  File "D:\Softwares\Python 3.6.0\lib\tkinter\ttk.py", line 614, in __init__
Widget.__init__(self, master, "ttk::button", kw)
  File "D:\Softwares\Python 3.6.0\lib\tkinter\ttk.py", line 559, in __init__
tkinter.Widget.__init__(self, master, widgetname, kw=kw)
  File "D:\Softwares\Python 3.6.0\lib\tkinter\__init__.py", line 2293, in __init__
(widgetName, self._w) + extra + self._options(cnf))
_tkinter.TclError: NULL main window

I have no idea what the problem is. I have trying to find answer for 4 hours and basically gave up.

Also, I don't want to use tkinter's messagebox feature because I don't want the exclamation mark image and I want to include multiple checkboxs inside the popup window later on.

Answer 1

I found 3 mistakes

• use Toplevel() instead of Tk() to create second/third window
• command= expects callback - function name without ()
  (but you use popupBonusWindow.destroy())
• don't mix pack() and grid() in one window or frame
  (but you use grid() and pack() in popup)

But you can also use built-in messageboxes like showinfo()

import tkinter as tk
from tkinter import ttk
from tkinter.messagebox import showinfo

def popup_bonus():
    win = tk.Toplevel()
    win.wm_title("Window")

    l = tk.Label(win, text="Input")
    l.grid(row=0, column=0)

    b = ttk.Button(win, text="Okay", command=win.destroy)
    b.grid(row=1, column=0)

def popup_showinfo():
    showinfo("Window", "Hello World!")

class Application(ttk.Frame):

    def __init__(self, master):
        ttk.Frame.__init__(self, master)
        self.pack()

        self.button_bonus = ttk.Button(self, text="Bonuses", command=popup_bonus)
        self.button_bonus.pack()

        self.button_showinfo = ttk.Button(self, text="Show Info", command=popup_showinfo)
        self.button_showinfo.pack()

root = tk.Tk()

app = Application(root)

root.mainloop()

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BTW: I put it on page: Tkinter: How to create popup Window or Messagebox