Multiprocessing queue in py2.7

Terry Reedy tjreedy at udel.edu
Tue Mar 28 15:38:38 EDT 2017


On 3/28/2017 2:51 PM, Frank Miles wrote:
> 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()
> # ---------------

Cut and pasted, this runs as specified on 2.7.13 on Win 10

> 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 says that the arg bound to q in f is an int rather than a Queue. 
Are you sure that you posted the code that you ran?

> 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!




-- 
Terry Jan Reedy



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