title: call multiprocessing in class method Python
body: <p>Initially, I have a class to store some processed values and re-use those with its other methods. </p>
  
  <p>The problem is when i tried to divide the class method into multiple process to speed up, python spawned processes but it seems didn't work (as I saw in Task Manager that only 1 process was running) and result is never delivered. </p>
  
  <p>I did couple of search and found that pathos.multiprocessing can do this instead but I wonder if standard library can solve this problems?</p>
  
  <pre><code>from multiprocessing import Pool
  
  class A():
      def __init__(self, vl):
          self.vl = vl
      def cal(self, nb):
          return nb * self.vl
      def run(self, dt):
          t = Pool(processes=4)
          rs = t.map(self.cal, dt)
          t.close()
          return t
  
  a = A(2)
  
  a.run(list(range(10)))
  </code></pre>