Is there a way to have a regular class modify a Tkinter class?

Question

I know that you can have a Tkinter class access another Tkinter class (How to access variables from different classes in tkinter?) But im looking for a way to have a regular class, to call functions / modify attributes from a Tkinter class.

import tkinter as tk
import tkinter.ttk as ttk


class Main(tk.Tk):
    def __init__(self, *args, **kwargs):
        tk.Tk.__init__(self, *args, **kwargs)

        self.geometry("1000x750+125+100")
        self.configure(bg="#272c34")
        self.resizable(False, False)
        self.frames = {}
        main_page_frame = tk.Frame(self)
        main_page_frame.pack(side="top", fill="both", expand=True)
        main_page_frame.grid_rowconfigure(0, weight=1)
        main_page_frame.grid_columnconfigure(0, weight=1)
        self.frames = {}
        self.my_label = tk.Label(self, text="old text")
        self.my_label.place(x=200, y=250)
        for F in (main_page, second_page):
            frame = F(main_page_frame, self)
            self.frames[F] = frame
            frame.grid(row=0, column=0, sticky="nsew")
        self.show_frame(main_page)

    def update(self):
        self.my_label.configure(text="New text!")

    def show_frame(self, cont):
        frame = self.frames[cont]
        frame.event_generate("<<ShowFrame>>")
        frame.tkraise()

    def get_page(self, page_class):
        return self.frames[page_class]

class Music:
    def __init__(self, controller):
        self.controller = controller
    song = "Song!"
    album = "Album!"

    def change_album(self):
        self.controller.update(Main)

everyones_music = Music(controller=Main)

class main_page(tk.Frame):
    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        self.controller = controller
        self.configure(bg="#272c34")
        y = tk.Label(self, text="main_page!")
        x = tk.Button(self, text="View second:", command=lambda: self.controller.show_frame(second_page))
        x.place(x=100, y=100)
        y.place(x=250, y=100)
        new_button = tk.Button(self, text='Change the variable', command=lambda: everyones_music.change_album())
        new_button.place(x=100, y=150)
        

class second_page(tk.Frame):
    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        self.configure(bg="#272c34")
        self.me = tk.Label(self, text=everyones_music.album)
        self.me.place(x=200, y=100)
        self.but = tk.Button(self, text="UPdate ??", command=self.update_is)
        self.but.place(x=100, y=100)

    def update_is(self):
        print(everyones_music.album)
        self.me.configure(text=everyones_music.album)


main_app = Main()
main_app.mainloop()

Essentially, I want the instance of class Music to be able to modify, or call functions in a Tkinter class. Specifically, function "change_album" should have like:

    def change_album(self):
        self.album = "new album!
        second_page.update_is()

Do I want an instance for each page? Does the class Music need to have a way to access the controller and modify properties from there? It is important that there is only one instance of Music, as required for the program.

In normal practice, it is not recommended to call `second_page.update_is()` inside `Music.change_album()`. I would suggest to call `everyones_music.change_album()` inside `second_page.update_is()` instead. — acw1668, Jul 12 '22 at 04:55
Problem with that is that I need to be able to modify the Music class, and have those changes reflected on the Tkinter second_page class. Do you know if this would be any different if instead of a Tkinter class, it was a frame based on the class 'Main'? it would be able to interact with controller and whatnot right? — NedNoodleHead, Jul 12 '22 at 18:53
You can easily make a class inheriting from a tkinter class and define a function with your own name or a name already used by tkinter. Then, instead of using the tkinter class name, you can just use your class name. This is how to write a class changing an imported class. — OmegaO333, Jul 13 '22 at 01:53

score 0 · Accepted Answer · answered Jul 19 '22 at 16:03

In the code you posted in the second version of your question, you are setting the controller incorrectly here:

everyones_music = Music(controller=Main)

The above sets the controller to the class Main rather than to an instance of Main. The controller needs to be the instance - in this case, main_app.

You also make a similar problem of passing the class when calling update here:

self.controller.update(Main)

The problem is, you have a chicken and the egg problem in the code as written. Music needs an instance of Main, but Main requires that the instance of Music already exists. More correctly, second_page is instantiated by Main and the instance of second_page requires that everyones_music has been defined.

You need to make sure you don't have a circular dependency. You can do that by either removing the controller argument from Music.__init__, or you can make second_page not require that the controller is defined in its __init__.

Let's do the first solution. To do that, you can rewrite the Music class to not require a controller:

class Music:
    def __init__(self, controller=None):
        self.controller = controller
    song = "Song!"
    album = "Album!"

    def change_album(self):
        if self.controller is not None:
            self.controller.update()

everyones_music = Music()

Then, inside Main.__init__ you can assign self to the controller of everyones_music:

class Main(tk.Tk):
    def __init__(self, *args, **kwargs):
        tk.Tk.__init__(self, *args, **kwargs)

        everyones_music.controller = self
        ...

With that, your code should work.

Is there a way to have a regular class modify a Tkinter class?

1 Answers1