Question

I started programming in Python on Monday. I have enjoyed learning it. But I am stuck trying to understand how to avoid recursion when switching between tkinter menus! I am sure this is a very basic question, and I appreciate you tolerating my ignorance on this subject, but I have been unable to find an answer elsewhere.

What I am now doing is, eventually, giving me the error: RuntimeError: maximum recursion depth exceeded while calling a Python object

This is the pattern I am currently using. UPDATED: The code below is now a full, isolated copy reproducing the problem I am facing! 😀

from tkinter import *

def mainmenu():
    global frame, root

    frame.destroy()

    frame = Frame()
    frame.pack()

    button1 = Button(frame, text="anothermenulikethis", command = anothermenulikethis)
    button2 = Button(frame, text="anothermenulikethis", command = anothermenulikethis)
    button3 = Button(frame, text="mainmenu", command = mainmenu)

    button1.pack(side=LEFT)
    button2.pack(side=LEFT)
    button3.pack(side=LEFT)

    root.mainloop()

def anothermenulikethis():
    global frame, root

    frame.destroy()

    frame = Frame()
    frame.pack()

    button1 = Button(frame, text="mainmenu", command = mainmenu)
    button2 = Button(frame, text="mainmenu", command = mainmenu)
    button3 = Button(frame, text="anothermenulikethis", command = anothermenulikethis)

    button1.pack(side=LEFT)
    button2.pack(side=LEFT)
    button3.pack(side=LEFT)

    root.mainloop()

root = Tk()
root.title("Recursive Menu Problem Isolation")
root.geometry("1200x600")
frame = Frame()

mainmenu()

And it all works fine, until its inevitable failure from maximum recursion depth. If anyone can suggest a better way of doing things, or has a link to an example of a better way of doing this, I am eager to learn.

PS: I have looked at and tried increasing the recursion depth, but I feel that is a poor man’s solution to what is a fundamental problem with my approach.

Thank you in advance, everyone.

As requested, here is the traceback:

Exception in Tkinter callback
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/tkinter/__init__.py", line 1399, in __call__
    return self.func(*args)
  File "/Users/diligentstudent/Desktop/menutest.py", line 11, in mainmenu
    button1 = Button(frame, text="anothermenulikethis", command = anothermenulikethis)
  File "/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/tkinter/__init__.py", line 2028, in __init__
    Widget.__init__(self, master, 'button', cnf, kw)
  File "/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/tkinter/__init__.py", line 1958, in __init__
    (widgetName, self._w) + extra + self._options(cnf))
  File "/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/tkinter/__init__.py", line 1043, in _options
    v = self._register(v)
  File "/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/tkinter/__init__.py", line 1079, in _register
    f = CallWrapper(func, subst, self).__call__
RuntimeError: maximum recursion depth exceeded

Answer 1

Only one mainloop() is needed to handle a tkinter GUI.

With that said, I think you just need an example of the class structure:

from tkinter import Tk,Button

class Application(Tk):

    def say_hi(self):
        print('Hello world?!')

    def close_app(self):
        self.destroy()

    def create_Widgets(self):
        self.quitButton = Button(self, width=12, text='Quit', bg='tan',
                    command=self.close_app)
        self.quitButton.grid(row=0, column=0, padx=8, pady=8)

        self.helloButton = Button(self, width=12, text='Hello',
                    command=self.say_hi)
        self.helloButton.grid(row=0, column=1, padx=8, pady=8)

    def __init__(self):
        Tk.__init__(self)
        self.title('Hello world!')
        self.create_Widgets()

app = Application()
app.mainloop()

To avoid possible conflicts with other modules, some people prefer importing like this
(clearly stating where everything comes from):

import tkinter as tk

class Application(tk.Tk):

    def __init__(self):
        tk.Tk.__init__(self)
        self.title('Hello world!')

        self.quitButton = tk.Button(self, width=12, text='Quit', bg='tan',
                    command=self.close_app)
        self.quitButton.grid(row=0, column=0, padx=8, pady=8)

        self.helloButton = tk.Button(self, width=12, text='Hello',
                    command=self.say_hi)
        self.helloButton.grid(row=0, column=1, padx=8, pady=8)

    def say_hi(self):
        print('Hello world?!')

    def close_app(self):
        self.destroy()

app = Application()
app.mainloop()

And as you can see, creating the widgets can easily happen in the __init__

---

I decided to make a more practical / educational example based on what I’ve learned in the past month. While doing so I had a bit of a revelation: not everything requires a self. prefix in a class! This is especially true with a tkinter class, because you aren’t manipulating it as an object in the main program. Mostly you need the self. prefix when you are going to use something in a method later. The previous examples display how anything (like the buttons) can receive a self. prefix, even when completely unnecessary.

Some things this example will show:

• pack() and grid() can be used in the same GUI as long as they don’t share a master.

• A Text widget can be made to not expand when the font size changes.

• How to toggle a bold tag on and off of selected text.

• How to truly center a GUI on the screen. (more information here)

• How to make a Toplevel window appear in the same location relative to the main window.

• Two ways to prevent a Toplevel window from being destroyed, so it only needs to be created once.

• Make ctrl+a (select all) function properly.

import tkinter as tk
import tkFont

class Application(tk.Tk):

    def __init__(self):
        tk.Tk.__init__(self)
        self.title('T-Pad')

    # Menubar

        menubar = tk.Menu(self)

        filemenu = tk.Menu(menubar, tearoff=0)
        filemenu.add_command(label="Exit", command=self.close_app)
        menubar.add_cascade(label="File", menu=filemenu)

        formatmenu = tk.Menu(menubar, tearoff=0)
        formatmenu.add_command(label="Font", command=self.show_sizeWin)
        menubar.add_cascade(label="Format", menu=formatmenu)

        self.config(menu=menubar)

    # Bold Button

        boldButton = tk.Button(self, width=12, text='Bold',
                                command=self.make_bold)
        boldButton.pack()

    # Text widget, its font and frame

        self.defaultFont = tkFont.Font(name="defFont")

        textFrame = tk.Frame(self, borderwidth=1, relief="sunken",
                             width=600, height=600)

        textFrame.grid_propagate(False) # ensures a consistent GUI size
        textFrame.pack(side="bottom", fill="both", expand=True)


        self.mText = tk.Text(textFrame, width=48, height=24, wrap='word',
                            font="defFont")
        self.mText.grid(row=0, column=0, sticky="nsew")

    # Scrollbar and config

        tScrollbar = tk.Scrollbar(textFrame, command=self.mText.yview)
        tScrollbar.grid(row=0, column=1, sticky='nsew', pady=1)

        self.mText.config(yscrollcommand=tScrollbar.set)

    # Stretchable

        textFrame.grid_rowconfigure(0, weight=1)
        textFrame.grid_columnconfigure(0, weight=1)

    # Bold Tag

        self.bold_font = tkFont.Font(self.mText, self.mText.cget("font"))
        self.bold_font.configure(weight="bold")
        self.mText.tag_configure("bt", font=self.bold_font)

    # Center main window

        self.update_idletasks()

        xp = (self.winfo_screenwidth() / 2) - (self.winfo_width() / 2) - 8
        yp = (self.winfo_screenheight() / 2) - (self.winfo_height() / 2) - 30
        self.geometry('{0}x{1}+{2}+{3}'.format(self.winfo_width(), self.winfo_height(),
                                                                                xp, yp))

    # Font Size Window (notice that self.sizeWin is given an alias)

        sizeWin = self.sizeWin = tk.Toplevel(self, bd=4, relief='ridge')

        self.sizeList = tk.Listbox(sizeWin, width=10, height=17, bd=4,
                                font=("Times", "16"), relief='sunken')

        self.sizeList.grid()

        doneButton = tk.Button(sizeWin, text='Done', command=sizeWin.withdraw)
        doneButton.grid()

        for num in range(8,25):
            self.sizeList.insert('end', num)

        sizeWin.withdraw()

        sizeWin.overrideredirect(True) # No outerframe!
        # Below is another way to prevent a TopLevel window from being destroyed.
        # sizeWin.protocol("WM_DELETE_WINDOW", self.callback)

    # Bindings
        # Double click a font size in the Listbox
        self.sizeList.bind("<Double-Button-1>", self.choose_size)
        self.bind_class("Text", "<Control-a>", self.select_all)

##    def callback(self):
##        self.sizeWin.withdraw()

    def select_all(self, event):
        self.mText.tag_add("sel","1.0","end-1c")

    def choose_size(self, event=None):
        size_retrieved = self.sizeList.get('active')
        self.defaultFont.configure(size=size_retrieved)
        self.bold_font.configure(size=size_retrieved)

    def show_sizeWin(self):
        self.sizeWin.deiconify()
        xpos = self.winfo_rootx() - self.sizeWin.winfo_width() - 8
        ypos = self.winfo_rooty()
        self.sizeWin.geometry('{0}x{1}+{2}+{3}'.format(self.sizeWin.winfo_width(),
                                                self.sizeWin.winfo_height(), xpos, ypos))

    def make_bold(self):
        try:
            current_tags = self.mText.tag_names("sel.first")
            if "bt" in current_tags:
                self.mText.tag_remove("bt", "sel.first", "sel.last")
            else:
                self.mText.tag_add("bt", "sel.first", "sel.last")
        except tk.TclError:
            pass

    def close_app(self):
        self.destroy()

app = Application()
app.mainloop()