[IPython-User] IPython TaskClient map(): UnpickleableError???

Fernando Perez fperez.net@gmail....
Sun Sep 26 19:14:58 CDT 2010


Hi Frank,

for some reason this email only showed up today on the list... I saw
similar behavior on some other scipy.org-hosted lists, so their server
seems to have  had a strange hiccup.

On Mon, Sep 20, 2010 at 4:20 AM, Frank Horowitz
<frank.horowitz@uwa.edu.au> wrote:
> Hi All,
>
> I'm trying to jam some moderately complicated data structures down the wire to the collection of engines, but am seeing the following error crop up:
>
> UnpickleableError: Cannot pickle <type 'str'> objects
>
> This is in response to a TaskClient instance's map() being called on a function with a single (tuple) argument where the sequence is being fed from a list.
>
> I've done the obvious, and tried pickle and cPickle directly on strings, and those *do* work --- much as you'd expect. I suspect this is something within the guts of Twisted...
>
> Any clues as to what might be causing this and/or how to avoid it?

That's a very, very odd error.  Do you know what's in the specific
string that is throwing this exception?  The most depressing part is
that if I google for your error message in quotes (to ensure I don't
get other unpckle error hits), the *only* hit from google is this very
thread!  It's always a bad sign when the entire google index only
returns your own questions back, and it's pretty rare to see a
*single* hit query these days:

1 result (0.26 seconds)
Search Results

   1.
      IPython TaskClient map(): UnpickleableError???
      Sep 20, 2010 ... IPython TaskClient map(): UnpickleableError?
... seeing the following error crop up: UnpickleableError: Cannot
pickle <type 'str'> objects ...
      permalink.gmane.org/gmane.comp.python.ipython.user/5294 - Cached

Ouch.

If you can isolate the string causing the traceback, or provide a
self-contained small test to reproduce the problem, we might be able
to track down who inside twisted is causing this.  It's also possible
(and I'd venture to say even likely) that the real error is something
else, and Twisted may be re-raising the wrong exception.

Regards,

f


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