import tkinter as tk
class MyApp(object):
  def __init__(self, parent):
    self.rootframe = tk.Frame(parent)
    self.rootframe.pack()
    self.setupUI()
  def setupUI(self):
    tk.Label(self.rootframe, text='标签').pack()
if __name__ == '__main__':
  root = tk.Tk()
  MyApp(root) # 注意这句
  root.mainloop()

import tkinter as tk
class MyApp(object):
  def __init__(self, parent, **kwargs):
    self.root = parent
    self.root.config(**kwargs)
    self.setupUI()
  def setupUI(self):
    tk.Label(self.root, text = '标签').pack()
if __name__ == '__main__':
  root = tk.Tk()
  app = test(root)
  root.mainloop()

import tkinter as tk
class MyApp(tk.Tk):
  def __init__(self):
    super().__init__()
    self.setupUI()
  def setupUI(self):
    tk.Label(self, text='标签').pack()
if __name__ == '__main__':
  MyApp().mainloop()

import tkinter as tk
class MyApp(tk.Frame):
  def __init__(self, parent=None):
    super().__init__(parent)
    self.pack()
    self.setupUI()
  def setupUI(self):
    tk.Label(self, text='标签').pack()
if __name__ == '__main__':
  MyApp(tk.Tk()).mainloop()
  #MyApp().mainloop() # 也可以这样

import tkinter as tk
class MyApp(tk.Frame):
  def __init__(self):
    super().__init__()
    self.pack()
    self.setupUI()
  def setupUI(self):
    tk.Label(self, text='标签').pack()
if __name__ == '__main__': 
  MyApp().mainloop()