Multiprocessing queue in py2.7

Frank Miles fpm at u.washington.edu
Tue Mar 28 14:51:04 EDT 2017


I tried running a bit of example code from the py2.7 docs
  (16.6.1.2. Exchanging objects between processes)
only to have it fail.  The code is simply:
# ------------  
from multiprocessing import Process, Queue

def f(q):
    q.put([42, None, 'hello'])

if __name__ == '__main__':
    q = Queue()
    p = Process(target=f, args=(q,))
    p.start()
    print q.get()    # prints "[42, None, 'hello']"
    p.join()
# ---------------
But what happens is f() fails:

Traceback (most recent call last):
  File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
    self.run()
  File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
    self._target(*self._args, **self._kwargs)
  File "x.py", line 4, in f
    q.put([42, None, "Hello"])
AttributeError: 'int' object has no attribute 'put'

This is on a Debian jessie host, though eventually it needs to
run on a raspberry pi 3 {and uses other library code that needs
py2.7}.

Thanks in advance for those marvelous clues!

   -F


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