Message249100
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). |
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Date |
User |
Action |
Args |
2015-08-25 02:54:32 | rhettinger | set | recipients:
+ rhettinger, Samuel Isaacson |
2015-08-25 02:54:32 | rhettinger | set | messageid: <1440471272.88.0.197023135588.issue24931@psf.upfronthosting.co.za> |
2015-08-25 02:54:32 | rhettinger | link | issue24931 messages |
2015-08-25 02:54:32 | rhettinger | create | |
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