ImportError: No module named copy_reg pickle

just an interactive python session to show that you don't need any particular code to have this problem:

do something like this on a windows machine

Python 2.4.1 (#65, Mar 30 2005, 09:13:57) [MSC v.1310 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import pickle, re
>>> empty_string = re.compile("^$")
>>> pickle.dump([empty_string,1,1.23,'abc'], file('m:/mario/test-b.dump','wb'))
>>> pickle.dump([empty_string,1,1.23,'abc'], file('m:/mario/test-t.dump','wt'))
>>> 

and then try to retrieve the data from a linux box

Python 2.6.2 (release26-maint, Apr 19 2009, 01:56:41) 
[GCC 4.3.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import pickle
>>> pickle.load(file('/home/mario/.gvfs/transfer on 192.168.0.4/mario/test-b.dump'))
/usr/lib/python2.6/pickle.py:1124: DeprecationWarning: The sre module is deprecated, please import re.
  __import__(module)
[<_sre.SRE_Pattern object at 0xb7d42420>, 1, 1.23, 'abc']
>>> pickle.load(file('/home/mario/.gvfs/transfer on 192.168.0.4/mario/test-t.dump'))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.6/pickle.py", line 1370, in load
    return Unpickler(file).load()
  File "/usr/lib/python2.6/pickle.py", line 858, in load
    dispatch[key](self)
  File "/usr/lib/python2.6/pickle.py", line 1090, in load_global
    klass = self.find_class(module, name)
  File "/usr/lib/python2.6/pickle.py", line 1124, in find_class
    __import__(module)
ImportError: No module named sre
>>> 

the error message can be even more confusing if you are just pickling base types. this is what I get with the list [12, 1.2, '']:

ValueError: insecure string pickle

It seems this might be caused by my method of exporting the pickled object.

This bug report seens to suggest that my issue can be resolved by exporting to a file writen in binary mode. I'm going to give this a go now and see if this solves my issue.

UPDATE: This works. The solution is to make sure you export your pickled object to a file open in binary mode, even if you are using the default protocol 0 (commonly referred to as being "text")

Correct code based on orignal example in question:

file = open("test.txt", 'wb')
thing = {'a': 1, 'b':2}
cPickle.dump(thing, file)

Also, simply running dos2unix (under linux) over the (windows-created) pickle file solved the problem for me. (Haven't tried the open mode 'wb' thing.) Dan