title: Python mutiprocessing pool with partial arguments
body: <p>So I'm trying to follow the example here:
  <a href="https://stackoverflow.com/questions/5442910/python-multiprocessing-pool-map-for-multiple-arguments">Python multiprocessing pool.map for multiple arguments</a></p>
  
  <p>What if I have three arguments and I need the third fixed to a value, e.g. some thing like this but it doesn't work. Raise TypeError saying partial_merge() takes exactly 2 arguments but only 1 given.</p>
  
  <pre><code>import multiprocessing
  from functools import partial
  
  
  def merge_names(a, b, c):
      return '{} &amp; {} &amp; {}'.format(a, b, c)
  
  
  if __name__ == '__main__':
      names = [('Brown', 'Wilson'), ('Bartlett', 'Rivera'), ('Molloy', 'Opie')]
      pool = multiprocessing.Pool(processes=3)
  
      results = pool.map(partial(merge_names, c='Hello'), names)
      pool.close()
      pool.join()
      print(results)
  </code></pre>