from multiprocessing.pool import Pool
from multiprocessing import current_process

def test_func():
    print("process = " + current_process().name)
    return current_process().name

def call_back(result):
    print("callack = " + current_process().name)
    return current_process().name

if __name__ == "__main__":
    current_process().name = "MainThread"
    pool = Pool(processes=5)
    result = pool.apply_async(test_func, callback=call_back).get()

def call_back(result):
    print("callack = " + current_process().name)
    return current_process().name

class TestClass:
    def __init__(self):
        pass

    def test_f(self):
        print("process = " + current_process().name)
        return current_process().name

if __name__ == "__main__":
    m = TestClass()
    current_process().name = "MainThread"
    pool = Pool(processes=5)
    result = pool.apply_async(m.test_f, callback=call_back).get()

Exception in thread Thread-2:
Traceback (most recent call last):
  File "C:\Python32\lib\threading.py", line 740, in _bootstrap_inner
    self.run()
  File "C:\Python32\lib\threading.py", line 693, in run
    self._target(*self._args, **self._kwargs)
  File "C:\Python32\lib\multiprocessing\pool.py", line 342, in _handle_tasks
    put(task)
_pickle.PicklingError: Can't pickle <class 'method'>: attribute lookup builtins.method failed