title: Is it possible to spawn a process inside a thread in Python?
body: <p>I'm wrting a program that spawns a process and restarts the process on certain conditions. For example, if a child process doesn't send data anymore to the mother process, for a certain period of time, I want the mother process to terminate the child process and restart it. I thought I could use a thread to recieve data from a child process and restart the child process, but it doesn't work the way I thought.</p>
  
  <pre><code>import numpy as np
  import multiprocessing as mp
  import threading
  import time
  from apscheduler.schedulers.background import BackgroundScheduler
  
  pipe_in, pipe_out = mp.Pipe()
  
  class Mother():
      def __init__(self):
          self.pipe_out = pipe_out
  
          self.proc = mp.Process(target = self.test_func, args=(pipe_in, ))
          self.proc.start()
  
          self.thread = threading.Thread(target=self.thread_reciever, args=(self.pipe_out, ))
          self.thread.start()
  
      def thread_reciever(self, pipe_out):
          while True:
              value = pipe_out.recv()
  
              print(value)
              if value == 5:
                  self.proc.terminate()
                  time.sleep(2)
                  self.proc = mp.Process(target = self.test_func)
                  self.proc.start()
  
      def test_func(self, pipe_in):
          for i in range(10):
              pipe_in.send(i)
              time.sleep(1)
  
  
  if __name__ == '__main__':
      r = Mother()
  </code></pre>
  
  <p>It prints out this error.</p>
  
  <pre><code>D:\&gt;d:\python36-32\python.exe temp06.py
      0
  1
  2
  3
  4
  5
  Exception in thread Thread-1:
  Traceback (most recent call last):
  File "d:\python36-32\lib\threading.py", line 916, in _bootstrap_inner
      self.run()
  File "d:\python36-32\lib\threading.py", line 864, in run
      self._target(*self._args, **self._kwargs)
  File "temp06.py", line 28, in thread_reciever
      self.proc.start()
  File "d:\python36-32\lib\multiprocessing\process.py", line 105, in start
      self._popen = self._Popen(self)
  File "d:\python36-32\lib\multiprocessing\context.py", line 223, in _Popen
      return _default_context.get_context().Process._Popen(process_obj)
  File "d:\python36-32\lib\multiprocessing\context.py", line 322, in _Popen
      return Popen(process_obj)
  File "d:\python36-32\lib\multiprocessing\popen_spawn_win32.py", line 65, in __init__
      reduction.dump(process_obj, to_child)
  File "d:\python36-32\lib\multiprocessing\reduction.py", line 60, in dump
      ForkingPickler(file, protocol).dump(obj)
  TypeError: can't pickle _thread.lock objects
  
  
  D:\&gt;Traceback (most recent call last):
  File "&lt;string&gt;", line 1, in &lt;module&gt;
  File "d:\python36-32\lib\multiprocessing\spawn.py", line 99, in spawn_main
      new_handle = reduction.steal_handle(parent_pid, pipe_handle)
  File "d:\python36-32\lib\multiprocessing\reduction.py", line 82, in steal_handle
      _winapi.PROCESS_DUP_HANDLE, False, source_pid)
  OSError: [WinError 87]
  </code></pre>
  
  <p>How could I start and terminate a process inside a thread? (I'm using a thread because it can synchronously recieve data from a different process) Or are there any other ways to do this job?</p>
  
  <p><strong>test_func as a global function</strong></p>
  
  <pre><code>import numpy as np
  import multiprocessing as mp
  import threading
  import time
  from apscheduler.schedulers.background import BackgroundScheduler
  
  pipe_in, pipe_out = mp.Pipe()  
  
  def test_func( pipe_in):
      for i in range(10):
          pipe_in.send(i)
          time.sleep(1)
  
  class Mother():
      def __init__(self):
          self.pipe_out = pipe_out
          mp.freeze_support()
          self.proc = mp.Process(target = test_func, args=(pipe_in, ))
          self.proc.start()
  
          self.thread = threading.Thread(target=self.thread_reciever, args=(self.pipe_out, ))
          self.thread.start()
  
      def thread_reciever(self, pipe_out):
          while True:
              value = pipe_out.recv()
  
              print(value)
              if value == 5:
                  self.proc.terminate()
                  time.sleep(2)
                  mp.freeze_support()
                  self.proc = mp.Process(target = test_func, args=(pipe_in,))
                  self.proc.start()
  
  
  if __name__ == '__main__':
  
      r = Mother()
  </code></pre>
  
  <p>OUTPUT</p>
  
  <pre><code>D:\&gt; d:\python36-32\python.exe temp06.py
  0
  1
  2
  3
  4
  5
  Traceback (most recent call last):
  File "&lt;string&gt;", line 1, in &lt;module&gt;
  File "d:\python36-32\lib\multiprocessing\spawn.py", line 105, in spawn_main
      exitcode = _main(fd)
  File "d:\python36-32\lib\multiprocessing\spawn.py", line 115, in _main
      self = reduction.pickle.load(from_parent)
  AttributeError: Can't get attribute 'test_func' on &lt;module '__main__' (built-in)&gt;
  </code></pre>