Created on 2012-10-28 08:04 by arigo, last changed 2012-10-31 18:14 by python-dev. This issue is now closed.
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| x.py | arigo, 2012-10-28 08:04 | |||
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| msg174009 - (view) | Author: Armin Rigo (arigo) *  |
Date: 2012-10-28 08:04 | |
The implementation of dict.fromkeys() assumes that the new dictionary is empty. That's not the case if we tweak __new__. Attached example shows 'dictresize(mp, 0)' being called with 'mp' being dictionary of 10 items. This causes an infinite uninterruptible loop. |
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| msg174129 - (view) | Author: Benjamin Peterson (benjamin.peterson) * |
Date: 2012-10-29 16:44 | |
I wonder what the semantics should be. I would like to just clear the dictionary that is returned from __new__ but you're also allowed to return custom classes from __new__ which we might not know how to clear. |
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| msg174140 - (view) | Author: Armin Rigo (arigo) * |
Date: 2012-10-29 18:49 | |
In case of doubt, see the source code of PyPy :-)
w_dict = space.call_function(w_type)
for w_key in space.listview(w_keys):
space.setitem(w_dict, w_key, w_fill)
(Seriously more compact.) No clear there...
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| msg174141 - (view) | Author: Armin Rigo (arigo) * |
Date: 2012-10-29 18:56 | |
Joke apart, you could check and complain if the object returned is an instance of 'dict' and is not empty. Otherwise just accept it. I think complaining is better than picking either of the two behaviors in this case. |
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| msg174160 - (view) | Author: Benjamin Peterson (benjamin.peterson) * |
Date: 2012-10-29 23:05 | |
That's still inconsistent, though, since we wouldn't complain if __new__ returns a user defined object. |
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| msg174352 - (view) | Author: Roundup Robot (python-dev) | Date: 2012-10-31 18:14 | |
New changeset a965eac352ec by Benjamin Peterson in branch '3.2': only fast-path fromkeys() when the constructor returns a empty dict (closes #16345) http://hg.python.org/cpython/rev/a965eac352ec New changeset b68da8f2ed95 by Benjamin Peterson in branch '3.3': merge 3.2 (#16345) http://hg.python.org/cpython/rev/b68da8f2ed95 New changeset 411d52192062 by Benjamin Peterson in branch 'default': merge 3.3 (#16345) http://hg.python.org/cpython/rev/411d52192062 New changeset 6a582cdfee41 by Benjamin Peterson in branch '2.7': only fast-path fromkeys() when the constructor returns a empty dict (closes #16345) http://hg.python.org/cpython/rev/6a582cdfee41 |
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| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2012-10-31 18:14:19 | python-dev | set | status: open -> closed nosy: + python-dev messages: + msg174352 resolution: fixed stage: needs patch -> resolved |
| 2012-10-29 23:05:13 | benjamin.peterson | set | messages: + msg174160 |
| 2012-10-29 18:56:21 | arigo | set | messages: + msg174141 |
| 2012-10-29 18:49:47 | arigo | set | messages: + msg174140 |
| 2012-10-29 16:44:11 | benjamin.peterson | set | messages: + msg174129 |
| 2012-10-29 13:02:36 | jcea | set | nosy:
+ jcea |
| 2012-10-28 08:16:42 | alex | set | nosy:
+ alex |
| 2012-10-28 08:10:42 | ezio.melotti | set | nosy:
+ benjamin.peterson, ezio.melotti stage: needs patch type: behavior versions: - Python 3.1 |
| 2012-10-28 08:04:26 | arigo | create | |