I need to make a function that can kill all processes owned by user and later to start few.

My main problem is that I cannot figure how to check if all processes were killed, and if there are still running processes, to retry for 1-2 times to kill them, and then return error. I want to use only python code.

Here is my code:

```
import os
import pwd

def pkill(user):
    pids = []
    user_pids = []
    uid = pwd.getpwnam(user).pw_uid
# get all PID 
    for i in os.listdir('/proc'):
        if i.isdigit():
            pids.append(i)
# test if PID is owned by user
    for i in pids:
        puid = os.stat(os.path.join('/proc', i)).st_uid
        if puid == uid:
            user_pids.append(i)
# print len(user_pids)
# check of PID still exist and kill it
    for i in user_pids:
        if os.path.exists(os.path.join('/proc',i)):
            try:
                os.kill(int(i), 15)
            except OSError: 

```

Thank you