Need to call class method from different class without initialization of the first class or some other way around it

Question

I have a small problem with my code.

There are two classes. First one creates a window with a Options button. Upon clicking the button, the second class is called and creates another window with an Ok button. Let's say there is also a checkbox, which changes the background color to black or something like that. After clicking the button, whatever changes were made in the options are stored into a file and the second window is closed.

All of this works fine. My problem is that now I need to call method update_init from the first class that will apply those changes to the MainWindow. The code below shows my first solution to this problem, but from what I understand, by using second mainloop I create second thread, which should be avoided.

class MainWindow:

    def __init__(self, master):
        self.master = master
        self.options_btn = tk.Button(self.master, text="Options", command=self.open_options)
        self.options_btn.pack()
        self.options_window = None

    def open_options(self):
        options_master = tk.Toplevel()
        self.options_window = OptionsWindow(options_master)
        options_master.mainloop()
        lst = meta_load()   # loads changes from a file
        self.update_init(lst)

    def update_init(self, lst):
        #code


class OptionsWindow:

    def __init__(self, master):
        self.master = master
        self.ok_btn = tk.Button(self.master, text="OK", command=self.update_meta)
        self.ok_btn.pack()

    def update_meta(self):
        meta_save(12)  # saves changes into a file
        self.master.destroy()

main_master = tk.Tk()
main_master.minsize(width=1280, height=720)
b = MainWindow(main_master)
main_master.mainloop()

My second solution was to just put both classes into one, but the code is quite messy if I do so. Can I somehow call the method update_init (which is in the MainWindow class) from the OptionsWindow class without initializing new MainWindow class window? Or is there any other way to deal with this? I would appreciate any help.

I am sorry if this is too specific, I've tried to make it as general as possible, but it's a very specific problem and I couldn't find much information about it anywhere on the internet.

Answer 1

In general you can call a class method from anywhere you want and pass anything to it without initialisation of that class's instance, thanks to objective nature of python, but beware of self dependencies! Although, I don't think that's a good practice.

class A:
    def __init__(self):
        self.foo = 'foo'

    def return_foo(self):
        return self.foo


class B:
    def __init__(self):
        self.bar = 'bar'
        print('Ha-ha Im inited!')

    def return_bar(self):
        try:
            return self.bar
        except AttributeError:
            return 'bar'


def test():
    a = A()
    # b = B()
    return_bar = getattr(B, 'return_bar', None)
    if callable(return_bar):
        print('%s%s' % (a.return_foo(), return_bar(None)))


test()

Links:

• getattr
• callable