如何在根TopLevel下的Python Tkinter框架中布局窗口小部件

Here is the code:

这是代码：

class Window(Frame):
    def __init__(self, master = None):
        Frame.__init__(self, master)
        self.master = master
        self.init_window()
    def init_window(self):
        self.master.title('GUI')

        row = 0
        self.s_date_label = Label(self, text = 'Start Date: ')
        self.s_date_label.grid(row=row, column=0, sticky = W)
        self.start_date = Entry(self, bd=1)
        self.start_date.grid(row=row, column=1, sticky = W)
        self.s_date_label2 = Label(self, text = 'example: 20160101')
        self.s_date_label2.grid(row=row, column=2, sticky = W)

        self.datetype_var = IntVar()
        R1 = Radiobutton(root, text="20160101", variable=self.datetype_var, value=8)
        R1.grid(row=row, column=1, sticky = W)
        R1.select()
        R2 = Radiobutton(root, text="201601", variable=self.datetype_var, value=6)
        R2.grid(row=row, column=2, sticky = W)
        R3 = Radiobutton(root, text="2016", variable=self.datetype_var, value=4)
        R3.grid(row=row, column=3, sticky = W)

root = Tk()
root.geometry('600x400')

app = Window(root)

root.mainloop()
class Window(Frame)