root@cpc304:~# cat yoba.py
import os


pid = os.fork()
if pid:

    print("parent")
    os.waitpid(pid, 0)

else:

    print("child")
root@cpc304:~# python yoba.py
parent
child
root@cpc304:~# python3 --version
Python 3.4.3
root@cpc304:~# python3 yoba.py
parent
Traceback (most recent call last):
  File "yoba.py", line 8, in <module>
    os.waitpid(pid, 0)
ChildProcessError: [Errno 10] No child processes
root@cpc304:~#