use Python to pass a list of objects as pool map arguments

Question

I am experiencing with Python Multiprocessing and got stuck with passing a list of object as pool.map arguments. The following codes print [None, None] instead of actual names. Can anybody shed some light on it?

from multiprocessing import Pool

class Item:
  def __init__(self, firstname, lastname):
    self.firstname = firstname
    self.lastname = lastname

def get_items():
  items = []
  names = ['Joe Smith', 'Rick Harvard']

  for name in names:
      item = Item(name.split(' ')[0], name.split(' ')[1])
      items.append(item)

  return items

def f(name):
    print(name.firstname, name.lastname)
    
if __name__ == '__main__':
  p = Pool(16)
  print(p.map(f, get_items()))
  p.close()
  p.join()

"print [None, None] ": This is correct, you call def f(... two times and def f(... return two times None. — stovfl
– stovfl, Commented Oct 7, 2019 at 18:19
Did you say: print(name.... in def f(... did not show up? — stovfl
– stovfl, Commented Oct 7, 2019 at 18:27

יהוידע שטינמץ · Accepted Answer · 2019-10-07 18:53:06Z

1

The print method returns None and you call it twice

change your f function to

def f(name):
    return name.firstname, name.lastname

answered Oct 7, 2019 at 18:53

יהוידע שטינמץ

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1 Comment

Don W. Over a year ago

Thank you. Worked.

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