Get process ID of the foreground window

Question

I'm trying to build a time tracker in Python, that records the screen time of applications I'm using. Approach that I use to get the PID of foreground window works fine most of the time:

import psutil
import win32gui
import win32process

while True:
    try:
        time.sleep(0.5)

        pid1 = win32process.GetWindowThreadProcessId(win32gui.GetForegroundWindow())
        process1 = psutil.Process(pid1[-1]).name()

        time.sleep(0.5)
    
        pid2 = win32process.GetWindowThreadProcessId(win32gui.GetForegroundWindow())
        process2 = psutil.Process(pid2[-1]).name()
    
        if process1 != process2:    
            print(process2)
    
    except ValueError or psutil.NoSuchProcess or ProcessLookupError as error:
        print(error)

But sometimes GetWindowThreadProcessId (line 7) returns a weird PID, sometimes negative:

pid must be a positive integer (got -571069920)
pid must be a positive integer (got -571069920)
pid must be a positive integer (got -571069920)
pid must be a positive integer (got -571069920)
pid must be a positive integer (got -571069920)

...while in my case the largest PID on my system was around 18000.

It happens randomly, mostly when using Chrome, if I close and reopen the window, it's PID is normal again, and I can get it's process name normally.

Does someone know why it is happening or recommend an alternative approach?

I tried reinstalling the libraries.

Answer 1

Found the problem.

Sometimes GetForegroundWindow thinks that the foreground window is System Idle Process, then GetWindowThreadProcessId returns a list of to PIDs corresponding to that process - [0 (always valid), {some big number} (always invalid)], while the other processes have the first PID always invalid (this is why to get the correct PID I use pid[-1])