报错：
_tkinter.TclError: cannot use geometry manager pack inside . which already has slaves managed by grid
原因：
一个程序中，只能使用一种布局，否则会报上面的错误。
python3 tkinter报错：_tkinter.TclError: cannot use geometry manager pack inside . which already has slaves managed by grid
原文：https://www.cnblogs.com/zrmw/p/10337993.html
