If that process belongs to the same user the checking process, you can just try to kill it. If you use signal 0, kill will not send anything but still allow you to tell if the process is available.
From kill(2):
If sig is 0, then no signal is sent, but error checking is still
performed; this can be used to check for the existence of a process ID
or process group ID.
This should propagate appropriately to python's methods.
