python: start a Multiprocessing process on wxbutton click

Question

I have a wxpython app running, and I was wondering if I could start another instance of the app as a result of a button click when the previous ones continue to run?

something like : Start a wxpython app -> click on a button -> and the event spawns another process (a multiprocessing process) that starts another instance of this same app while the first one keeps on running?

I just wanted to know whether it is feasible because when I start a simple process inside a button click event handling, like

def start_new_button(self,event):
    import multiprocessing
    worker2 = multiprocessing.Process(name = 'worker2', target = self.new)
    worker2.start()
def new():
    pass

it throws error

Traceback (most recent call last):
  File "main.py", line 470, in start_new_button
    worker2.start()
  File "C:\Python27\lib\multiprocessing\process.py", line 130, in start
    self._popen = Popen(self)
  File "C:\Python27\lib\multiprocessing\forking.py", line 277, in __init__
    dump(process_obj, to_child, HIGHEST_PROTOCOL)
  File "C:\Python27\lib\multiprocessing\forking.py", line 199, in dump
    ForkingPickler(file, protocol).dump(obj)
  File "C:\Python27\lib\pickle.py", line 224, in dump
    self.save(obj)
  File "C:\Python27\lib\pickle.py", line 331, in save
    self.save_reduce(obj=obj, *rv)
  File "C:\Python27\lib\pickle.py", line 419, in save_reduce
    save(state)
  File "C:\Python27\lib\pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "C:\Python27\lib\pickle.py", line 649, in save_dict
    self._batch_setitems(obj.iteritems())
  File "C:\Python27\lib\pickle.py", line 681, in _batch_setitems
    save(v)
  File "C:\Python27\lib\pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "C:\Python27\lib\multiprocessing\forking.py", line 67, in dispatcher
    self.save_reduce(obj=obj, *rv)
  File "C:\Python27\lib\pickle.py", line 401, in save_reduce
    save(args)
  File "C:\Python27\lib\pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "C:\Python27\lib\pickle.py", line 548, in save_tuple
    save(element)
  File "C:\Python27\lib\pickle.py", line 331, in save
    self.save_reduce(obj=obj, *rv)
  File "C:\Python27\lib\pickle.py", line 419, in save_reduce
    save(state)
  File "C:\Python27\lib\pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "C:\Python27\lib\pickle.py", line 649, in save_dict
    self._batch_setitems(obj.iteritems())
  File "C:\Python27\lib\pickle.py", line 681, in _batch_setitems
    save(v)
  File "C:\Python27\lib\pickle.py", line 331, in save
    self.save_reduce(obj=obj, *rv)
  File "C:\Python27\lib\pickle.py", line 419, in save_reduce
    save(state)
  File "C:\Python27\lib\pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "C:\Python27\lib\pickle.py", line 649, in save_dict
    self._batch_setitems(obj.iteritems())
  File "C:\Python27\lib\pickle.py", line 686, in _batch_setitems
    save(v)
  File "C:\Python27\lib\pickle.py", line 331, in save
    self.save_reduce(obj=obj, *rv)
  File "C:\Python27\lib\pickle.py", line 396, in save_reduce
    save(cls)
  File "C:\Python27\lib\pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "C:\Python27\lib\pickle.py", line 748, in save_global
    (obj, module, name))
pickle.PicklingError: Can't pickle <type 'PySwigObject'>: it's not found as __bu
iltin__.PySwigObject
C:\Python27\lib\site-packages\mpltools\style\__init__.py:42: FutureWarning:

    The style-sheet functionality in mpltools has been integrated into
    Matplotlib >= 1.4. This module will be removed in a future release.

    Note that style-sheets used by `matplotlib.style` use the standard
    Matplotlib rc-file syntax instead of the INI format used by `mpltools`.
    This mostly means un-quoting strings and changing '=' to ':'.


  """, FutureWarning)
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "C:\Python27\lib\multiprocessing\forking.py", line 381, in main
    self = load(from_parent)
  File "C:\Python27\lib\pickle.py", line 1378, in load
    return Unpickler(file).load()
  File "C:\Python27\lib\pickle.py", line 858, in load
    dispatch[key](self)
  File "C:\Python27\lib\pickle.py", line 880, in load_eof
    raise EOFError
EOFError

Am I going on the right path?

Iam using python 2.7 with wx 3.0.2.0 on windows 7

Answer 1

Python multiprocessing uses the pickle module to pass the information to the new process. The pickle documentation describes, what can be pickled and unpickled . With self.new you are trying to pass an instance method which cannot be pickled.

Try passing a non-instance method to multiprocessing.Process() :

class YourButtonClass:
    def start_new_button(self,event):
        import multiprocessing
        worker2 = multiprocessing.Process(name = 'worker2', target = new)
        worker2.start()

def new():
    pass