Raymond Hettinger added the comment:
For __dict__, I'm not sure what the right behavior should by for subclasses
that don't define __slots__. In Python 3, the __dict__ is returning the dict
for the subclass. This might be the correct and most desirable behavior:
>>> class Point(namedtuple('_Point', ['x', 'y'])):
pass
>>> a = Point(3, 4)
>>> a.w = 5
>>> a.__dict__
{'w': 5}
If we leave the __dict__ behavior as is in Py3, then we still need to get
_asdict() back to its documented behavior. For that, we would need to
disconnect it from __dict__ by restoring the Py2.7 code for _asdict():
def _asdict(self):
'Return a new OrderedDict which maps field names to their values'
return OrderedDict(zip(self._fields, self))
All this needs to be thought-out carefully. Putting in __dict__ support
originally looked like a bugfix to get vars() working correctly, but it caused
problems with pickling which then led to the addition of __getnewargs__. It
seems that defining __dict__ leads to problems no matter how you do it.
My inclination is to remove __dict__ and __getewargs__ from the namedtuple
definition entirely and return to a simpler state of affairs that is easier to
reason about and less likely to lead to unexpected behaviors like the one in
this bug report.
One note: using the Py2.7 namedtuple code in Python3 still doesn't restore the
old behavior. Something else in the language appears to have changed (causing
the subclasses' __dict__ to take precedence over the inherited __dict__
property).
----------
priority: normal -> high
versions: +Python 3.5, Python 3.6
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<http://bugs.python.org/issue24931>
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