New submission from liugang <[email protected]>:
-- code 1
import pickle
class MyException():
def __init__(self, desc, *, item):
super().__init__()
self.desc = desc
self.item = item
def __getnewargs_ex__(self):
print('called in {}.__getnewargs_ex__'.format(self.__class__.__name__))
return (self.desc,), self.__dict__
e = MyException('testing', item='cpu')
s = pickle.dumps(e, protocol=-1)
x = pickle.loads(s)
-- code 2
import pickle
class MyException(Exception):
def __init__(self, desc, *, item):
super().__init__()
self.desc = desc
self.item = item
def __getnewargs_ex__(self):
print('called in {}.__getnewargs_ex__'.format(self.__class__.__name__))
return (self.desc,), self.__dict__
e = MyException('testing', item='cpu')
s = pickle.dumps(e, protocol=-1)
x = pickle.loads(s)
in code 1, the class is inherted from object, __getnewargs_ex__ is called and
the returned args, kwargs are passed to __new__/__init__ to construct object
when pickling.
in code 2, the class is inherted from Exception, __getnewargs_ex__ is not
called, and rasie an exception of "TypeError: __init__() missing 1 required
positional argument: 'desc'"
I think this is not python issue, it should be the right behavior of Exception.
I want to known why it is, and how to implement the logic in code 2 (passing
keyword only parameter to __new__/__init__ when pickling for class inherted
from Exception)
----------
components: Library (Lib)
messages: 347178
nosy: liugang93
priority: normal
severity: normal
status: open
title: pickling instance which inherited from Exception with keyword only
parameter
type: behavior
versions: Python 3.5
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Python tracker <[email protected]>
<https://bugs.python.org/issue37489>
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