New submission from Crusader Ky <[email protected]>:
As of CPython 3.8.0b1:
If one pickles an object that is defined in the __main__ module, sends it to a
subinterpreter as bytes, and then tries unpickling it there, it fails saying
that __main__ doesn't define it.
import _xxsubinterpreters as interpreters
import pickle
class C:
pass
c = C()
interp_id = interpreters.create()
c_bytes = pickle.dumps(c)
interpreters.run_string(
interp_id,
"import pickle; pickle.loads(c_bytes)",
shared={"c_bytes": c_bytes},
)
If the above is executed directly with the python command-line, it fails. If
it's imported from another module, it works.
One would expected behaviour compatible with sub-processes spawned with the
spawn method, where the__main__ of the parent process is visible to the
subprocess too.
Workarounds:
1 - define everything that must be pickled in an imported module
2 - use CloudPickle
----------
messages: 345680
nosy: Crusader Ky, eric.snow
priority: normal
severity: normal
status: open
title: _xxsubinterpreters: Can't unpickle objects defined in __main__
type: behavior
versions: Python 3.9
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Python tracker <[email protected]>
<https://bugs.python.org/issue37292>
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