pyqt-tutorial-by-mitu 教程源自： https://www.youtube.com/watch?v=G5BWgnEBW6U&list=PLq9fAEr-k3NwCFg6HlJ5MPrvYumXKIAyF&index=2 和 https://www.youtube.com/watch?v=ygf-cdbx6CU&list=PLLPsLcbaFY21h8bnBBig8Y0YgOdGpzIjm&index=135