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| From | 88888 Dihedral <dihedral88888@googlemail.com> |
| Newsgroups | comp.lang.python |
| Subject | Re: order independent hash? |
| Date | Fri, 2 Dec 2011 09:00:40 -0800 (PST) |
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On Friday, December 2, 2011 5:53:47 PM UTC+8, Hrvoje Niksic wrote:
> Chris Angelico <ros...@gmail.com> writes:
>
> >> The hash can grow with (k,v) pairs accumulated in the run time.
> >> An auto memory management mechanism is required for a hash of a non-fixed size of (k,v) pairs.
> >
> > That's a hash table
>
> In many contexts "hash table" is shortened to "hash" when there is no
> ambiguity. This is especially popular among Perl programmers where the
> equivalent of dict is called a hash.
>
> > Although strictly speaking, isn't that "Python dicts are implemented
> > as hash tables in CPython"? Or is the hashtable implementation
> > mandated?
>
> It's pretty much mandated because of the __hash__ protocol.
I agree with you. When a hash is inserted with (k,v1) and then (k,v2)
such that v1!=v2, there are several possibilities to handle this situation
in programming:
1. v2 just replaces v1 with or without a message
2. the programmer can delete the (k,v1) entry and then insert a (k, (v1,v2))
entry.
3. the programmer initializes a tuple of (v1,v2), and then delete the (k,v1)
entry to be replaced by a (k,(v1,v2)) entry.
Hashes of hashes are really powerful in Python to be used to build a relational
DB of thousands of thousands of objects or records in a piece of cake.
A similar hash library in C is to be used everywhere is not difficult at all.
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Re: order independent hash? Peter Otten <__peter__@web.de> - 2011-11-30 13:47 +0100
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-01 07:35 -0800
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-01 07:35 -0800
Re: order independent hash? Dave Angel <d@davea.name> - 2011-12-01 10:52 -0500
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-01 08:17 -0800
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-01 08:17 -0800
Re: order independent hash? Chris Angelico <rosuav@gmail.com> - 2011-12-02 03:18 +1100
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-01 20:29 -0800
Re: order independent hash? Chris Angelico <rosuav@gmail.com> - 2011-12-02 16:00 +1100
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-01 21:48 -0800
Re: order independent hash? Lie Ryan <lie.1296@gmail.com> - 2011-12-05 00:40 +1100
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-01 21:48 -0800
Re: order independent hash? Roel Schroeven <rschroev_nospam_ml@fastmail.fm> - 2011-12-04 14:41 +0100
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-04 07:39 -0800
Re: order independent hash? Ian Kelly <ian.g.kelly@gmail.com> - 2011-12-04 10:41 -0700
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-04 10:06 -0800
Re: order independent hash? Ian Kelly <ian.g.kelly@gmail.com> - 2011-12-04 13:13 -0700
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-04 15:17 -0800
Re: order independent hash? Matt Joiner <anacrolix@gmail.com> - 2011-12-05 10:21 +1100
Re: order independent hash? Ian Kelly <ian.g.kelly@gmail.com> - 2011-12-04 16:24 -0700
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-04 16:52 -0800
Re: order independent hash? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-12-05 02:00 +0000
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-04 16:52 -0800
Re: order independent hash? Lie Ryan <lie.1296@gmail.com> - 2011-12-05 12:59 +1100
Re: order independent hash? Ethan Furman <ethan@stoneleaf.us> - 2011-12-04 18:08 -0800
Re: order independent hash? Ben Finney <ben+python@benfinney.id.au> - 2011-12-05 15:52 +1100
Re: order independent hash? Matt Joiner <anacrolix@gmail.com> - 2011-12-05 14:02 +1100
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-06 21:24 -0800
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-06 21:24 -0800
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-04 15:17 -0800
Re: order independent hash? Terry Reedy <tjreedy@udel.edu> - 2011-12-04 19:28 -0500
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-04 10:06 -0800
Re: order independent hash? Hrvoje Niksic <hniksic@xemacs.org> - 2011-12-02 10:53 +0100
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-02 03:48 -0800
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-02 09:00 -0800
Re: order independent hash? Terry Reedy <tjreedy@udel.edu> - 2011-12-02 16:40 -0500
Re: order independent hash? Hrvoje Niksic <hniksic@xemacs.org> - 2011-12-04 14:55 +0100
Re: order independent hash? Chris Angelico <rosuav@gmail.com> - 2011-12-05 01:08 +1100
Re: order independent hash? Hrvoje Niksic <hniksic@xemacs.org> - 2011-12-07 14:28 +0100
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-07 09:48 -0800
Re: order independent hash? Tim Chase <python.list@tim.thechases.com> - 2011-12-04 12:57 -0600
Re: order independent hash? Hrvoje Niksic <hniksic@xemacs.org> - 2011-12-08 10:30 +0100
Re: order independent hash? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-12-09 11:27 +0000
Re: order independent hash? Hrvoje Niksic <hniksic@xemacs.org> - 2011-12-09 17:51 +0100
Re: order independent hash? Chris Angelico <rosuav@gmail.com> - 2011-12-10 04:13 +1100
Re: order independent hash? Lie Ryan <lie.1296@gmail.com> - 2011-12-11 10:58 +1100
Re: order independent hash? Chris Angelico <rosuav@gmail.com> - 2011-12-11 11:17 +1100
Re: order independent hash? Lie Ryan <lie.1296@gmail.com> - 2011-12-11 14:04 +1100
Re: order independent hash? Lie Ryan <lie.1296@gmail.com> - 2011-12-05 00:29 +1100
Re: order independent hash? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-01 20:29 -0800
Re: order independent hash? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-12-02 04:33 +0000
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