from tkinter import *
class Application(Frame):
    """A GUI application"""

    def __init__(self,master):
        """Initialize the frame"""
        Frame.__init__(self,master)
        self.grid()
        self.widg()
    def widg(self):
        """create buttons"""
        self.btn1=Button(self, text="Button 1")
        self.btn1.grid()
        self.btn2=Button(self, text="Button 2")
        self.btn2.grid()
        self.btn3=Button(self, text="Button 3")
        self.btn3.grid()

root=Tk()
root.title("Buttons")
root.geometry("300x200")
app=Application(root)
root.mainloop()