matplotlib之__main__:1: UserWarning: Matplotlib is currently using agg, which is a non-GUI backend, so cannot show the figure.

如果遇到问题：

__main__:1: UserWarning: Matplotlib is currently using agg, which is a non-GUI backend, so cannot show the figure.

解决方案：

在程序中增加一条语句：

import matplotlib

matplotlib.use('TkAgg') （增加这条语句）