Is this bad programming practice in tkinter?

1. You will want to use classes as your application gets larger. Instead of having to wrap your mind around the entire code, you can concentrate on a class at a time.
2. You are not restricted to using only the methods in a class. Your code may utilize external functions or classes to get information or even modify arguments given to them.
3. No, that is how would probably display the information. Alternatively, you might use a file to output your results, and it may be possible to print to the console if it is present.

Example:

import tkinter
import random

class Application(tkinter.Frame):

    @classmethod
    def main(cls):
        root = tkinter.Tk()
        frame = cls(root)
        frame.grid()
        root.mainloop()

    def __init__(self, master=None, cnf={}, **kw):
        super().__init__(master, cnf, **kw)
        self.w = tkinter.Label(self, text="Hello, world!")
        self.w.grid()
        self.v = tkinter.Button(self, text="Press Me", command=self.click)
        self.v.grid()
        self.u = tkinter.Button(self, text="Me Too!",
                                command=lambda: external_mutator(self.w))
        self.u.grid()

    def click(self):
        self.w['text'] = external_function(3)

def external_function(ndigits):
    return round(random.random(), ndigits)

def external_mutator(widget):
    widget['text'] = external_function(6)
    print('Hello to you too!')  # shown on console if present

if __name__ == '__main__':
    Application.main()

---

Alternative to the main classmethod:

import tkinter
import random

class Main(tkinter.Tk):

    def __init__(self, screenName=None, baseName=None, className="Tk",
                 useTk=1, sync=0, use=None):
        super().__init__(screenName, baseName, className,
                         useTk, sync, use)
        frame = Application(self)
        frame.grid()
        self.mainloop()

class Application(tkinter.Frame):

    def __init__(self, master=None, cnf={}, **kw):
        super().__init__(master, cnf, **kw)
        self.w = tkinter.Label(self, text="Hello, world!")
        self.w.grid()
        self.v = tkinter.Button(self, text="Press Me", command=self.click)
        self.v.grid()
        self.u = tkinter.Button(self, text="Me Too!",
                                command=lambda: external_mutator(self.w))
        self.u.grid()

    def click(self):
        self.w['text'] = external_function(3)

def external_function(ndigits):
    return round(random.random(), ndigits)

def external_mutator(widget):
    widget['text'] = external_function(6)
    print('Hello to you too!')  # shown on console if present

if __name__ == '__main__':
    Main()