[issue29229] incompatible: unittest.mock.sentinel and multiprocessing.Pool.map()

[Jason Curtis]

Jason Curtis added the comment:

sounds right; closing as a duplicate of issue20804

--
resolution:  -> duplicate
status: open -> closed

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[issue29229] incompatible: unittest.mock.sentinel and multiprocessing.Pool.map()

[Davin Potts]

Davin Potts added the comment:

I think this should be regarded as a duplicate of issue20804 though discussion 
in issue14577 is also related/relevant.

--
superseder:  -> Sentinels identity lost when pickled (unittest.mock)

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[issue29229] incompatible: unittest.mock.sentinel and multiprocessing.Pool.map()

[Davin Potts]

Davin Potts added the comment:

This arises from the behavior of pickle (which is used by default in 
multiprocessing to serialize objects sent to / received from other processes in 
data exchanges), as seen with Python 3.6:

>>> import pickle
>>> x = pickle.dumps(mock.sentinel.foo)
>>> x
b'\x80\x03cunittest.mock\n_SentinelObject\nq\x00)\x81q\x01}q\x02X\x04\x00\x00\x00nameq\x03X\x03\x00\x00\x00fooq\x04sb.'
>>> pickle.loads(x)
sentinel.foo
>>> pickle.loads(x) == mock.sentinel.foo
False

--
nosy: +davin

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[issue29229] incompatible: unittest.mock.sentinel and multiprocessing.Pool.map()

[Jason Curtis]

New submission from Jason Curtis:

When a sentinel object from unittest.mock.sentinel is passed through a 
multiprocessing.Pool.map, I expect it to still be comparable. 

As a user, I'd like to be able to write a unit test using sentinels on my 
unparallelized code, and then see that the test still passes after I 
parallelize the code using multiprocessing, so that I can make use of sentinels 
in regression testing.


Example:
```
from unittest import mock
import multiprocessing


def identity(x):
return x

with multiprocessing.Pool() as pool:
multiprocessed = list(pool.map(identity, [mock.sentinel.foo]))

assert identity(mock.sentinel.foo) == mock.sentinel.foo  # Passes
assert multiprocessed[0] == mock.sentinel.foo  # Fails
```

--
components: Library (Lib)
messages: 285146
nosy: Jason Curtis
priority: normal
severity: normal
status: open
title: incompatible: unittest.mock.sentinel and multiprocessing.Pool.map()
type: behavior
versions: Python 3.4

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