[issue1733184] slice type is unhashable
Raymond Hettinger rhettin...@users.sourceforge.net added the comment: This needs to stay rejected. I'm unwilling to introduce special cases in the language just to support a peephole optimization. -- assignee: gvanrossum - rhettinger ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue1733184 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue1733184] slice type is unhashable
Guido van Rossum gu...@python.org added the comment: Did Alexander ever present his case to python-dev? -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue1733184 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue1733184] slice type is unhashable
L. Peter Deutsch [EMAIL PROTECTED] added the comment: Having now read messages 63380 and 63384, I agree with them: I would have withdrawn my proposal if it hadn't gotten rejected first. I do have a use case, but the workaround is pretty easy. _ Tracker [EMAIL PROTECTED] http://bugs.python.org/issue1733184 _ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue1733184] slice type is unhashable
Alexander Belopolsky [EMAIL PROTECTED] added the comment: I hate to flip-flop like this, but please consider my new arguments at issue2268. In short, slices being unhashable prevents storing them in the code object's const dictionary and thus prevents optimizing code involving const slices. Unless I hear strong opposition from the bug tracker forum, I plan to present some ideas on python-dev on how to make slices hashable while not enabling d[:]. _ Tracker [EMAIL PROTECTED] http://bugs.python.org/issue1733184 _ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue1733184] slice type is unhashable
Jean-Paul Calderone added the comment: I don't see the ability to use a slice as a dict key as particularly more surprising than the ability to use ints as dict keys. Someone who doesn't understand how dicts work can use either of these features to write broken programs. I have thought about that example and it's precisely the kind of thing I would like to work. The behavior is consistent with that of using any other immutable value as a key. I don't have a use case right now (and by admitting so may be dooming this change - but L. Peter Deutsch has one, I think) but there's no way I would ever benefit from the current behavior, whereas I _might_ be able to do something useful with the proposed behavior. _ Tracker [EMAIL PROTECTED] http://bugs.python.org/issue1733184 _ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue1733184] slice type is unhashable
Alexander Belopolsky added the comment: Note that L[:] and L[:] = [] are well-known idioms for making a copy of a list and emptying the list respectively. (For dictionaries we have D.copy() and D.clear().) Someone looking at x[:] or x[:] = [] should immediately recognize a list copy or clear operation. Having to think of whether x may be a dictionary would make such code very confusing. _ Tracker [EMAIL PROTECTED] http://bugs.python.org/issue1733184 _ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue1733184] slice type is unhashable
Changes by Raymond Hettinger: -- resolution: - rejected status: open - closed _ Tracker [EMAIL PROTECTED] http://bugs.python.org/issue1733184 _ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue1733184] slice type is unhashable
Alexander Belopolsky added the comment: Patch # 408326 was designed to make assignment to d[:] an error where d is a dictionary. See discussion starting at http://mail.python.org/pipermail/python-list/2001-March/072078.html . I think the only reason slice objects need to be comparable is only to suppress inheritance of the default hash from object. This RFE is ripe to be rejected. Slice objects are really meant to be internal structures and not passed around in the user's code. You can always use tuples instead of slices and convert the to slices with slice(*t) when needed. -- nosy: +belopolsky type: - feature request _ Tracker [EMAIL PROTECTED] http://bugs.python.org/issue1733184 _ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue1733184] slice type is unhashable
Raymond Hettinger added the comment: Guido, any thoughts? I'm +0 on making slices hashable -- no real harm from doing it -- not much benefit either. -- assignee: - gvanrossum nosy: +gvanrossum _ Tracker [EMAIL PROTECTED] http://bugs.python.org/issue1733184 _ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue1733184] slice type is unhashable
Alexander Belopolsky added the comment: In case I did not make my position clear in my previous post, I am -1 on this RFE. x[:] should mean slicing, not getitem. _ Tracker [EMAIL PROTECTED] http://bugs.python.org/issue1733184 _ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue1733184] slice type is unhashable
Jean-Paul Calderone added the comment: Slice objects are really meant to be internal structures and not passed around in the user's code. I don't know what they're meant to be, but they're certainly not internal. If you implement __getitem__, __setitem__, or __delitem__, then chances are Python is going to be passing slices to your code. That doesn't sound internal to me. Having hashable slices is nice. The repr() workaround has a major drawback in that it makes it difficult to use the extremely useful indices method of the slice type. -- nosy: +exarkun _ Tracker [EMAIL PROTECTED] http://bugs.python.org/issue1733184 _ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue1733184] slice type is unhashable
Guido van Rossum added the comment:
Alexander nailed my motivation.
Have the proponents for this change really thought through that making
slices hashable means that henceforth this code will work?
d = {}
d[:] = [1, 2, 3] # surprise here
print d # prints {slice(None, None, None): [1, 2, 3]}
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