mainwindow.py file is not executed

hello，I've been working on qtpyvcp lately. Use the mainwindow.ui file designed by qtdesigner, write some code in the py file, but it seems that the code in the py file is not executed.
Because I deliberately changed the py file wrong, but the UI interface is still working properly.
 

may be you need to add Property "Run executable", to be able to run this file.