使用tkinter设置一个按钮,将按钮放置在窗口最下方,则划线处的Python代码为?( )
from tkinter import * root = Tk() root.geometry('300x200') root.title('my window') btn1 = Button(root,text='按钮1',bg='red') __________ root.mainloop()
btn1.pack(side=TOP)
btn1.pack()
btn1.pack(side=BOTTOM)
btn1.pack(side='')