如何在子进程期间和之后做事情

I have a program that call to an subprogram. While the subprogram is running with Popen, I need the run button to be disable and the stop button to enable. However, because Popen opens a new process, things that are suppose to print after the program has finish will print out right away. I tried adding I have a program that call to an subprogram. Wh