Hello,

I've just run into a related issue. I have a python script, which starts an another python script using subprocess.Popen(). The parent script gets pid of the child and monitors up its activity through a database by this pid. The child script updates its activity in the database using the pid it gotten from os.getpid()

Both scripts live in a virtual environment.

It worked fine in Python 3.5 and stopped working after migration to Python 3.8.

My base Python location: D:\Python\Python38\pythonw.exe
Virtual Environment: D:\test\venv\Scripts\pythonw.exe

I have realized, that when I run the following from a command prompt:
D:\test\venv\Scripts\pythonw.exe test.py

2 processes with the different PIDs are created:
PID:                   97040
Parent PID:            12004  (cmd.exe)
Command Line:          D:\test\venv\Scripts\pythonw.exe test.py

PID:                   85548
Parent PID:            97040  (pythonw.exe)
Command Line:          D:\Python\Python38\pythonw.exe test.py

It is definitely a regression, and will potentially break a lot of applications expecting a child Python process to be a direct descendant of its parent.

Also it is a waste of system resources