Re: Dict when defining not returning multi value key error

From	Marko Rauhamaa <marko@pacujo.net>
Newsgroups	comp.lang.python
Subject	Re: Dict when defining not returning multi value key error
Date	2014-08-01 18:39 +0300
Organization	A noiseless patient Spider
Message-ID	<87vbqcnrrh.fsf@elektro.pacujo.net> (permalink)
References	(2 earlier) <mailman.12501.1406862741.18130.python-list@python.org> <53db11c1$0$29986$c3e8da3$5496439d@news.astraweb.com> <mailman.12503.1406866676.18130.python-list@python.org> <53db96bc$0$29986$c3e8da3$5496439d@news.astraweb.com> <mailman.12512.1406901485.18130.python-list@python.org>

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Chris Angelico <rosuav@gmail.com>:

>> but hash(x) == hash(y) does NOT imply that x == y.
>
> Hello, pigeonhole principle :) If this were false - that is, if equal
> hashes DID imply equal objects - it would be necessary to completely
> encode an object's state in its hash, and hashes would be impossibly
> large. This would, in fact, destroy their value completely.

Well, modern computing assumes precisely:

   hash(x) == hash(y) => x == y

That principle is at play with strong authentication (HTTPS et al),
version control (git et al),

A handful of bits uniquely identify an object regardless of its size.


Marko

Thread

Re: Dict when defining not returning multi value key error Dan Stromberg <drsalists@gmail.com> - 2014-07-31 20:12 -0700
  Re: Dict when defining not returning multi value key error Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-01 04:04 +0000
    Re: Dict when defining not returning multi value key error Ben Finney <ben+python@benfinney.id.au> - 2014-08-01 14:17 +1000
      Re: Dict when defining not returning multi value key error Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-01 13:31 +0000
        Re: Dict when defining not returning multi value key error Chris Angelico <rosuav@gmail.com> - 2014-08-01 23:57 +1000
          Re: Dict when defining not returning multi value key error Marko Rauhamaa <marko@pacujo.net> - 2014-08-01 18:39 +0300
            Re: Dict when defining not returning multi value key error Terry Reedy <tjreedy@udel.edu> - 2014-08-01 17:42 -0400
            Re: Dict when defining not returning multi value key error Chris Angelico <rosuav@gmail.com> - 2014-08-02 09:57 +1000
              Re: Dict when defining not returning multi value key error Marko Rauhamaa <marko@pacujo.net> - 2014-08-02 09:41 +0300
                Re: Dict when defining not returning multi value key error Marko Rauhamaa <marko@pacujo.net> - 2014-08-02 10:06 +0300
                Re: Dict when defining not returning multi value key error Chris Angelico <rosuav@gmail.com> - 2014-08-02 20:58 +1000
            Re: Dict when defining not returning multi value key error Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-02 11:47 +1000
              Re: Dict when defining not returning multi value key error Chris Angelico <rosuav@gmail.com> - 2014-08-02 12:13 +1000

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