[New-bugs-announce] [issue45112] Python exception object is different after pickle.loads and pickle.dumps

[Chen Zero]

New submission from Chen Zero <yonghengzero at gmail.com>:

Hi, when I'm trying to serialize/deserialize python exception object through pickle, I found that deserialize result is not the same as the original object...

My python version is 3.9.1, working os: macOS Big Sur 11.4

Here is minimum reproducing code example:

import pickle

class ExcA(Exception):
    def __init__(self, want):
        msg = "missing "
        msg += want
        super().__init__(msg)

ExcA('bb')   # this will output ExcA("missing bb"), which is good
pickle.loads(pickle.dumps(ExcA('bb')))  # this will output ExcA("missing missing bb"), which is different from `ExcA('bb')`

----------
files: screenshot.png
messages: 401128
nosy: yonghengzero
priority: normal
severity: normal
status: open
title: Python exception object is different after pickle.loads and pickle.dumps
type: behavior
versions: Python 3.9
Added file: https://bugs.python.org/file50262/screenshot.png

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue45112>
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