Multiprocessor objects with namedtuple - Etching Error

Question

I am having problems using namedtuples in objects that I want to use for multiprocessing. I get an etching error. I tried a couple of things from other stackoverflow posts, but I was not able to succeed. Here is the structure of my code:

package_main, test_module

 import myprogram.package_of_classes.data_object_module
 import ....obj_calculate

 class test(object):
       if __name__ == '__main__':
             my_obj=create_obj('myobject',['f1','f2'])
             input = multiprocessing.Queue()
             output = multiprocessing.Queue()
             input.put(my_obj)
             j=Process(target=obj_calculate, args=(input,output))
             j.start()

package_of_classes, data_object_module

 import collections
 import ....load_flat_file

 def get_ntuple_format(obj):
     nt_fields=''
     for fld in obj.fields:
         nt_fields=nt_fields+fld+', '
     nt_fields=nt_fields[0:-2]
     ntuple=collections.namedtuple('ntuple_format',nt_fields)
     return ntuple

 Class Data_obj:
    def __init__(self, name,fields):
        self.name=name
        self.fields=fields
        self.ntuple_form=get_ntuple_format(self)  

    def calculate(self):
        self.file_read('C:/files','division.txt')

    def file_read(self,data_directory,filename):
        output=load_flat_file(data_directory,filename,self.ntuple_form)
        self.data=output

utils_package, utils_module

def create_dataobj(name,fields):
    locals()[name]=Data_Obj(name,fields)
    return locals()[name]  

def obj_calculate(input,output):   
    obj=input.get()
    obj.calculate()
    output.put(obj)

loads_module

def load_flat_file(data_directory,filename,ntuple_form):
     csv.register_dialect('csvrd', delimiter='\t', quoting=csv.QUOTE_NONE)
     ListofTuples=[]
     with open(os.path.join(data_directory,filename), 'rb') as f:
          reader = csv.reader(f,'csvrd')
          for line in reader:
               if line:
                   ListofTuples.append(ntuple_form._make(line))
     return ListofTuples

And the error I get is:

PicklingError: PicklingError: Can't pickle  class '__main__ . ntuple_format: it not the same object as __ main __. ntuple_format

PS When I extracted this sample code from a large project, please ignore minor inconsistencies.

Answer 1

( , ), ( get_ntuple_format). , , .

, , , , . , dict.

Answer 2

, namedtuple, class, __main__.

>>> import dill as pickle
>>> import collections
>>> 
>>> thing = collections.namedtuple('thing', ['a','b'])
>>> pickle.loads(pickle.dumps(thing))
<class '__main__.thing'>

, .

>>> class Foo(object):
...   def bar(self, a, b):
...     thing = collections.namedtuple('thing', ['a','b'])     
...     thing.a = a 
...     thing.b = b
...     return thing 
... 
>>> f = Foo()
>>> q = f.bar(1,2)
>>> q.a
1
>>> q.b
2
>>> q._fields
('a', 'b')
>>> 
>>> pickle.loads(pickle.dumps(Foo.bar))
<unbound method Foo.bar>
>>> pickle.loads(pickle.dumps(f.bar))
<bound method Foo.bar of <__main__.Foo object at 0x10dbf5450>>

dill pickle.

dill : https://github.com/uqfoundation