homepage

Creating a namedtuple and an instance of the namedtuple in a function then returning the instance to the global namespace made the instance unpickleable, as in Issue25665.

I don't think this has anything to do with namedtuple; it's true whenever you create a class in an inner scope (rather than at module level). This is by design, and these restrictions are documented: https://docs.python.org/3.6/library/pickle.html#what-can-be-pickled-and-unpickled
For example, running this script:
 import pickle
 def my_func():
 class A:
 pass
 a = A()
 return a
 a = my_func()
 pickle.dumps(a)
produces:
 Traceback (most recent call last):
 File "test.py", line 11, in <module>
 pickle.dumps(a)
 AttributeError: Can't pickle local object 'my_func.<locals>.A'

My bad, I searched and found the issue, it very closely fit mine and the pickle module is new to me. I hadn't yet got through the details of pickling. Thanks for catching that.
Kurt
 From: Mark Dickinson <report@bugs.python.org>
 To: thedomesticdog@yahoo.com 
 Sent: Saturday, September 24, 2016 1:43 AM
 Subject: [issue28250] typing.NamedTuple instances are not picklable Two
Mark Dickinson added the comment:
I don't think this has anything to do with namedtuple; it's true whenever you create a class in an inner scope (rather than at module level). This is by design, and these restrictions are documented: https://docs.python.org/3.6/library/pickle.html#what-can-be-pickled-and-unpickled
For example, running this script:
  import pickle
  def my_func():
    class A:
      pass
    a = A()
    return a
  a = my_func()
  pickle.dumps(a)
produces:
  Traceback (most recent call last):
   File "test.py", line 11, in <module>
    pickle.dumps(a)
  AttributeError: Can't pickle local object 'my_func.<locals>.A'
----------
nosy: +mark.dickinson
resolution: -> not a bug
status: open -> closed
_______________________________________
Python tracker <report@bugs.python.org>
<http://bugs.python.org/issue28250>
_______________________________________