Python Multiprocessing Array initialization

Question

I'm trying to use Process Arrays in order to use an Array structure across multiple Processes, but cant seem to initialize the example:

from multiprocessing import Process, Lock
from multiprocessing.sharedctypes import Value, Array
from ctypes import Structure, c_double,c_char_p

class Point(Structure):
    _fields_ = [('x', c_double), ('y', c_double)]

class Call(Structure):
    _fields_ = [('participantId',c_char_p)]

def modify(n,s):
    n.value **= 2
    #x.value **= 2
    s.value = s.value.upper()
    #for a in A:
    #    a.x **= 2
    #    a.y **= 2

if __name__ == '__main__':
    lock = Lock()

    n = Value('i', 7)
   #x = Value(c_double, 1.0/3.0, lock=False)
    s = Array('c', 'hello world', lock=lock)
    A = Array(Call,['ebtirgnm-sqr7-h2fd-wa80-baoctu684qma'], lock=lock)
   #A = Array(Point, [(1.875,-6.25), (-5.75,2.0), (2.375,9.5)], lock=lock)

    p = Process(target=modify, args=(n,s))
    p.start()
    p.join()

    print n.value
  #  print x.value
    print s.value

I get an error when initializing my Array with Call Object in this line:

A = Array(Call,['ebtirgnm-sqr7-h2fd-wa80-baoctu684qma',], lock=lock)


/System/Library/Frameworks/Python.framework/Versions/2.7/bin/python /Users/gogasca/Documents/OpenSource/Development/Python/tpsEmulator/tpsEmulator/tools/Array.py
Traceback (most recent call last):
  File "/Users/gogasca/Documents/OpenSource/Development/Python/tpsEmulator/tpsEmulator/tools/Array.py", line 25, in <module>
    A = Array(Call,['1'], lock=lock)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/multiprocessing/sharedctypes.py", line 115, in Array
    obj = RawArray(typecode_or_type, size_or_initializer)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/multiprocessing/sharedctypes.py", line 89, in RawArray
    result.__init__(*size_or_initializer)
TypeError: expected Call instance, got str

I have tried:

  call1 = Call(["1"])
  ['1',]
  [('1')]
  [0]

No luck

Max Vyaznikov · Accepted Answer · 2014-12-18 11:57:18Z

2

There is an error here:

A = Array(Call,['ebtirgnm-sqr7-h2fd-wa80-baoctu684qma'], lock=lock)

Python is interpreting string as object, not arguments. It should be:

A = Array(Call,[('ebtirgnm-sqr7-h2fd-wa80-baoctu684qma',)], lock=lock)

Then python will interpret this as arguments. Same error is in examples:

call1 = Call(["1"])
['1',]
[('1')]
[0]

Let's trying to see what python thinks about last comma:

>>> print [('1')]
['1']
>>> print [('1',)]
[('1',)]

edited Dec 18, 2014 at 11:57

answered Dec 18, 2014 at 11:52

Max Vyaznikov

4,4352 gold badges13 silver badges10 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Python Multiprocessing Array initialization

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related