psutil.Process().ppid() works but .parent() doesn't

[harplife]

Summary

• OS: Windows 10
• Architecture: 64bit
• Psutil version: 5.8
• Python version: 3.7.4
• Type:

Description

I'm trying to write a program that finds ALL parent processes of a process.

My code is this:

import psutil

def print_process_info(proc_obj, proc_order=1):
    with proc_obj.oneshot():
        print(f'process order {proc_order}')
        print('name: ', proc_obj.name())
        print('pid: ', proc_obj.pid)
        print('status: ', proc_obj.status())
        print('exe: ', proc_obj.exe())
        try:
            parent_pid = proc_obj.ppid()
        except Exception as e:
            raise e
        else:
            print('parent id: ', parent_pid)
            try:
                parent = proc_obj.parent()
                #parent = psutil.Process(parent_pid)
            except psutil.NoSuchProcess:
                print(f'Unable to find parent, {parent_pid}')
            else:
                if parent is not None:
                    print('\nPrinting parent process info\n')
                    proc_order += 1
                    print_process_info(parent, proc_order=proc_order)
                else:
                    print(f'Unable to find parent, {parent_pid}')

p = psutil.Process()

The problem I've noticed:

Once this program goes to what I think is the top-level,
it still returns a parent pid - but won't access the parent process.

For example, running this code returns a log similar to this:

1. python, pid 49000, ppid 45636
2. python, pid 45636, ppid 40208
3. bash, pid 40208, ppid 21072
4. bash, pid 21072, ppid 54124
5. cmd, pid 54124, ppid 46588
6. git-bash, pid 46588, ppid 10116
7. explorer, pid 10116, ppid 10036

and then, it's unable to find a process with pid 10036.

Using .parent() simply returns None,
whereas .Process(ppid) returns an Exception NoSuchProcess.

My assumption for the cause of the problem is Access Permission,
but I'm confused because .ppid() should return with an Exception describing Access Denied if that was the case. This goes the same with .parent(), or .Process(ppid).

If this really is a problem related with access permission,

• why would it not say so?
• is there a way to get access permission?

If it's not, can anybody shed a light on what may be the problem?