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Groups > comp.lang.python > #48896
| References | (7 earlier) <565a1c8f-6fd9-4bab-9834-076eaea527f8@googlegroups.com> <kq23at$i39$1@dont-email.me> <7e1ed740-df18-4978-b11d-8ca9c4b5bd04@googlegroups.com> <kq2o0k$vng$1@dont-email.me> <46567a60-bb75-4f22-b968-bf3ccbf35afb@googlegroups.com> |
|---|---|
| Date | 2013-06-22 11:37 +1000 |
| Subject | Re: Default Value |
| From | Chris Angelico <rosuav@gmail.com> |
| Newsgroups | comp.lang.python |
| Message-ID | <mailman.3676.1371865068.3114.python-list@python.org> (permalink) |
On Sat, Jun 22, 2013 at 11:15 AM, Rick Johnson
<rantingrickjohnson@gmail.com> wrote:
> # Literal
> py> d = {[1]:2}
> Traceback (most recent call last):
> File "<pyshell#0>", line 1, in <module>
> d = {[1]:2}
> TypeError: unhashable type: 'list'
> # Symbol
> py> lst = [1]
> py> d = {lst:2}
> Traceback (most recent call last):
> File "<pyshell#2>", line 1, in <module>
> d = {lst:2}
> TypeError: unhashable type: 'list'
>
> Hmm, maybe only certain mutables work? Great, more esoteric
> rules! Feel free to enlighten me since i'm not going to
> waste one second of my time pursuing the docs just to learn
> about ANOTHER unintuitive PyWart i have no use for.
>>> class HashableList(list):
def __hash__(self):
return 42
>>> a=HashableList()
>>> a
[]
>>> a.append(1)
>>> a.append(2)
>>> a.append(3)
>>> a
[1, 2, 3]
>>> d={a:123}
>>> d
{[1, 2, 3]: 123}
>>> a.append(4)
>>> d[a]
123
It's nothing to do with mutability, all to do with hashability. And
you can pick a number of different ways of hashing these objects, like
going for the object's id(), or attempting to hash tuple(self) and
falling back on id(), or anything you like. Easy.
ChrisA
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Default Value Ahmed Abdulshafy <abdulshafy@gmail.com> - 2013-06-19 12:17 -0700
Re: Default Value Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2013-06-19 22:35 +0300
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-19 12:38 -0700
Re: Default Value rusi <rustompmody@gmail.com> - 2013-06-20 05:57 -0700
Re: Default Value Roy Smith <roy@panix.com> - 2013-06-20 09:19 -0400
Re: Default Value rusi <rustompmody@gmail.com> - 2013-06-20 06:31 -0700
Re: Default Value Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-21 00:17 +0000
Re: Default Value Roy Smith <roy@panix.com> - 2013-06-20 20:25 -0400
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-20 07:49 -0700
Re: Default Value Chris Angelico <rosuav@gmail.com> - 2013-06-21 01:38 +1000
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-20 11:05 -0700
Re: Default Value Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-21 00:57 +0000
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-20 20:16 -0700
Re: Default Value Chris Angelico <rosuav@gmail.com> - 2013-06-21 17:10 +1000
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-21 07:32 -0700
Re: Default Value Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-21 16:22 +0000
Re: Default Value Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-21 15:57 +0000
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-21 10:01 -0700
Re: Default Value Rotwang <sg552@hotmail.co.uk> - 2013-06-21 18:47 +0100
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-21 11:26 -0700
Re: Default Value Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-21 18:37 +0000
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-21 12:18 -0700
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-21 12:35 -0700
Re: Default Value Chris Angelico <rosuav@gmail.com> - 2013-06-22 05:07 +1000
Re: Default Value Neil Cerutti <neilc@norwich.edu> - 2013-06-21 19:20 +0000
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-21 13:27 -0700
Re: Default Value Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-22 01:31 +0000
Re: Default Value Chris Angelico <rosuav@gmail.com> - 2013-06-22 11:40 +1000
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-21 18:42 -0700
Re: Default Value MRAB <python@mrabarnett.plus.com> - 2013-06-22 03:04 +0100
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-21 19:32 -0700
Re: Default Value MRAB <python@mrabarnett.plus.com> - 2013-06-22 20:36 +0100
Re: Default Value Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-06-22 18:51 -0400
Re: Default Value rusi <rustompmody@gmail.com> - 2013-06-21 19:43 -0700
Re: Default Value Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-06-22 09:26 +0100
Re: Default Value MRAB <python@mrabarnett.plus.com> - 2013-06-21 20:25 +0100
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-21 13:44 -0700
Re: Default Value MRAB <python@mrabarnett.plus.com> - 2013-06-21 23:49 +0100
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-21 16:51 -0700
Re: Default Value MRAB <python@mrabarnett.plus.com> - 2013-06-22 02:54 +0100
Re: Default Value Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-22 01:15 +0000
Re: Default Value Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-21 19:27 -0600
Re: Default Value rusi <rustompmody@gmail.com> - 2013-06-21 19:32 -0700
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-21 19:55 -0700
Re: Default Value rusi <rustompmody@gmail.com> - 2013-06-21 23:23 -0700
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-22 08:07 -0700
Re: Default Value rusi <rustompmody@gmail.com> - 2013-06-22 08:31 -0700
Re: Default Value rusi <rustompmody@gmail.com> - 2013-06-22 09:11 -0700
Re: Default Value Grant Edwards <invalid@invalid.invalid> - 2013-06-24 14:22 +0000
Re: [SPAM] Re: Default Value MRAB <python@mrabarnett.plus.com> - 2013-06-24 16:22 +0100
Re: Default Value Chris Angelico <rosuav@gmail.com> - 2013-06-22 11:41 +1000
Re: Default Value Michael Torrie <torriem@gmail.com> - 2013-06-21 20:46 -0600
Re: Default Value Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-06-22 16:40 +0200
Re: Default Value Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-06-22 12:49 -0400
Re: Default Value Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-22 12:57 -0600
Re: Default Value Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-06-22 18:48 -0400
Re: Default Value Rotwang <sg552@hotmail.co.uk> - 2013-06-22 00:40 +0100
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-21 18:15 -0700
Re: Default Value Chris Angelico <rosuav@gmail.com> - 2013-06-22 11:37 +1000
Re: Default Value Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-21 19:42 -0600
Re: Default Value Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-21 19:38 -0600
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-21 19:40 -0700
Re: Default Value Rotwang <sg552@hotmail.co.uk> - 2013-06-22 03:01 +0100
Re: Default Value Chris Angelico <rosuav@gmail.com> - 2013-06-22 12:18 +1000
Re: Default Value Rotwang <sg552@hotmail.co.uk> - 2013-06-22 03:25 +0100
Re: Default Value Rotwang <sg552@hotmail.co.uk> - 2013-06-22 18:19 +0100
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-22 11:49 -0700
Re: Default Value Rotwang <sg552@hotmail.co.uk> - 2013-06-23 01:49 +0100
Re: Default Value rusi <rustompmody@gmail.com> - 2013-06-20 10:12 -0700
Re: Default Value Chris Angelico <rosuav@gmail.com> - 2013-06-21 03:19 +1000
Re: Default Value rusi <rustompmody@gmail.com> - 2013-06-20 10:30 -0700
Re: Default Value Ian Kelly <ian.g.kelly@gmail.com> - 2013-06-20 11:57 -0600
Re: Default Value rusi <rustompmody@gmail.com> - 2013-06-20 11:15 -0700
Re: Default Value Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-21 01:08 +0000
Re: Default Value Tim Chase <python.list@tim.thechases.com> - 2013-06-20 20:26 -0500
Re: Default Value Roy Smith <roy@panix.com> - 2013-06-20 21:40 -0400
Re: Default Value Tim Chase <python.list@tim.thechases.com> - 2013-06-20 21:02 -0500
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-20 11:07 -0700
Re: Default Value alex23 <wuwei23@gmail.com> - 2013-06-21 10:55 +1000
Re: Default Value 88888 Dihedral <dihedral88888@gmail.com> - 2013-06-20 19:18 -0700
Re: Default Value Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-21 02:26 +0000
Re: Default Value "Lefavor, Matthew (GSFC-582.0)[MICROTEL LLC]" <matthew.lefavor@nasa.gov> - 2013-06-20 17:28 -0500
Re: Default Value Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-21 08:17 -0700
Re: Default Value Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-21 01:28 +0000
Re: Default Value Gary Herron <gherron@digipen.edu> - 2013-06-19 12:57 -0700
Re: Default Value Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-20 01:17 +0000
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