from tkinter import *
class Duble(Frame):
    def __init(self, parent, *args, **kwargs):
        super().__init__(parent, *args, **kwargs)
        self.text = Text(self, width = 100, height=100, bg = 'white')
        self.text.insert('end', '\nПервая строка\nВторая строка\nТретья строка\nЧетвёртая строка')
        self.sidebar = Text(self, bg='magenta', width=30)
        self.text.pack(side=RIGHT, fill=BOTH, expand=True)
        self.sidebar.pack(side=LEFT, fill=Y)
class Applic(Tk):
    def __init__(self, parent=None, *args, **kwargs):
        super().__init__(parent, *args, **kwargs)
        self.duble = Duble(self)
        self.duble.pack(fill=BOTH, expand=True)
if __name__ == "__main__":
    applic = Applic()
    applic.mainloop()

 def __init(self, parent, *args, **kwargs):