Why am I getting access denyed when program is not running?

I have a simple piece of code taken mostly from this answer, with some adjustments:

import psutil

try:
    if "firefox.exe" in (p.name() for p in psutil.process_iter()):
        print('Firefox is running')
    else:
        print('Firefox is not running')
except Exception as e:
    print(e)

If Firefox is running when I run this code, it prints the expected Firefox is running. But if firefox isn’t running, I get psutil.AccessDenied (pid=9092) instead of the expected Firefox is not running.

I also noticed that if firefox.exe is misspelled, I get the AccessDenied error again. I could just print('Firefox is not running') inside the except block, but that doesn’t seem very smart.

Does anyone know why this is happening?

Answer

process_iter() allows you to specify the attributes that should be returned. So tell it to just return the names, and compare them.

if any(p.info['name'] == "firefox.exe" for p in psutil.process_iter(['name'])):

Got this from the documentation:

Find process by name