Re: Suggestion: make sequence and map interfaces more similar

From	Jussi Piitulainen <jussi.piitulainen@helsinki.fi>
Newsgroups	comp.lang.python
Subject	Re: Suggestion: make sequence and map interfaces more similar
Date	2016-03-30 17:38 +0300
Organization	A noiseless patient Spider
Message-ID	<lf54mbodo9w.fsf@ling.helsinki.fi> (permalink)
References	(9 earlier) <lf5d1qcuu47.fsf@ling.helsinki.fi> <mailman.192.1459335430.28225.python-list@python.org> <lf54mbous6w.fsf@ling.helsinki.fi> <56fbc650$0$1622$c3e8da3$5496439d@news.astraweb.com> <871t6sm8se.fsf@elektro.pacujo.net>

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Marko Rauhamaa writes:

> Steven D'Aprano:
>
>> On Wed, 30 Mar 2016 10:21 pm, Jussi Piitulainen wrote:
>>> Ok, safer to say that some many-to-one mappings are not surjective.
>>
>> Can you give an example of a Python dict which is not surjective?
>
> Depends on the codomain. The values() method gives the range.
>
> If you have an ordinary Python dictionary that maps strings to strings,
> it will be neither total nor surjective. Since there are strings that
> are not among the keys (not total) and there are strings that are not
> among the values (not surjective).
>
> You can of course equate keys() with the domain and values() with the
> range, in which case the whole discussion becomes nonsensical.
>
> However, a collections.defaultdict instance can be both total and
> surjective in the meaningful senses of the words.

The cited Wikipedia article uses "image" for what Marko here calls
"range" (unfortunately it also calls individual values "images" (and the
elements of the domain and codomain, "expressions"), and "range" is also
sometimes used to mean codomain :).

I'm just pointing this out because range aka image is a key concept
here, together with codomain.

<https://en.wikipedia.org/wiki/Bijection,_injection_and_surjection>

Thread

Re: Suggestion: make sequence and map interfaces more similar "Marco S." <mail.python.org@marco.sulla.e4ward.com> - 2016-03-27 20:01 +0200
  Re: Suggestion: make sequence and map interfaces more similar Steven D'Aprano <steve@pearwood.info> - 2016-03-28 12:05 +1100
    Re: Suggestion: make sequence and map interfaces more similar Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-03-29 16:08 +0200
    Re: Suggestion: make sequence and map interfaces more similar Chris Angelico <rosuav@gmail.com> - 2016-03-30 01:31 +1100
    Re: Suggestion: make sequence and map interfaces more similar Marco Sulla <mail.python.org@marco.sulla.e4ward.com> - 2016-03-30 00:29 +0200
    Re: Suggestion: make sequence and map interfaces more similar Terry Reedy <tjreedy@udel.edu> - 2016-03-29 20:55 -0400
    Re: Suggestion: make sequence and map interfaces more similar Chris Angelico <rosuav@gmail.com> - 2016-03-30 11:56 +1100
    Re: Suggestion: make sequence and map interfaces more similar Random832 <random832@fastmail.com> - 2016-03-29 23:38 -0400
      Re: Suggestion: make sequence and map interfaces more similar Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-03-30 16:43 +1100
        Re: Suggestion: make sequence and map interfaces more similar Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-03-30 16:57 +1100
        Re: Suggestion: make sequence and map interfaces more similar Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-03-30 10:12 +0300
          Re: Suggestion: make sequence and map interfaces more similar Steven D'Aprano <steve@pearwood.info> - 2016-03-30 21:17 +1100
            Re: Suggestion: make sequence and map interfaces more similar Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-03-30 13:28 +0300
              Re: Suggestion: make sequence and map interfaces more similar Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-03-30 12:34 +0200
                Re: Suggestion: make sequence and map interfaces more similar Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-03-30 13:57 +0300
              Re: Suggestion: make sequence and map interfaces more similar Steven D'Aprano <steve@pearwood.info> - 2016-03-30 23:22 +1100
                Re: Suggestion: make sequence and map interfaces more similar Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-03-30 15:12 +0200
                Re: Suggestion: make sequence and map interfaces more similar Steven D'Aprano <steve@pearwood.info> - 2016-03-31 02:56 +1100
                Re: Suggestion: make sequence and map interfaces more similar Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-03-30 21:07 +0200
                Re: Suggestion: make sequence and map interfaces more similar Steven D'Aprano <steve@pearwood.info> - 2016-03-31 13:40 +1100
                Re: Suggestion: make sequence and map interfaces more similar Paul Rubin <no.email@nospam.invalid> - 2016-03-30 19:45 -0700
                Re: Suggestion: make sequence and map interfaces more similar Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-03-31 17:45 +1100
                Re: Suggestion: make sequence and map interfaces more similar Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-03-31 09:52 +0200
                Re: Suggestion: make sequence and map interfaces more similar Steven D'Aprano <steve@pearwood.info> - 2016-03-31 21:36 +1100
                Re: Suggestion: make sequence and map interfaces more similar Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-03-31 12:51 +0200
                Re: Suggestion: make sequence and map interfaces more similar Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-03-31 13:22 +0200
                Re: Suggestion: make sequence and map interfaces more similar Chris Angelico <rosuav@gmail.com> - 2016-03-31 22:57 +1100
                Re: Suggestion: make sequence and map interfaces more similar Marko Rauhamaa <marko@pacujo.net> - 2016-03-31 15:36 +0300
                Re: Suggestion: make sequence and map interfaces more similar Chris Angelico <rosuav@gmail.com> - 2016-03-31 23:48 +1100
                Re: Suggestion: make sequence and map interfaces more similar Marko Rauhamaa <marko@pacujo.net> - 2016-03-31 17:02 +0300
                Re: Suggestion: make sequence and map interfaces more similar Michael Selik <michael.selik@gmail.com> - 2016-04-01 04:19 -0400
                Re: Suggestion: make sequence and map interfaces more similar Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-03-31 15:55 +0300
                Re: Suggestion: make sequence and map interfaces more similar Marko Rauhamaa <marko@pacujo.net> - 2016-03-31 17:19 +0300
                Re: Suggestion: make sequence and map interfaces more similar Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-03-31 15:08 +0200
                Re: Suggestion: make sequence and map interfaces more similar Rustom Mody <rustompmody@gmail.com> - 2016-03-31 06:42 -0700
                Re: Suggestion: make sequence and map interfaces more similar Chris Angelico <rosuav@gmail.com> - 2016-04-01 00:11 +1100
                Re: Suggestion: make sequence and map interfaces more similar Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-31 14:17 +0100
                Re: Suggestion: make sequence and map interfaces more similar Random832 <random832@fastmail.com> - 2016-03-31 09:27 -0400
                Re: Suggestion: make sequence and map interfaces more similar Marko Rauhamaa <marko@pacujo.net> - 2016-03-31 17:13 +0300
                Re: Suggestion: make sequence and map interfaces more similar Terry Reedy <tjreedy@udel.edu> - 2016-03-31 13:41 -0400
                Re: Suggestion: make sequence and map interfaces more similar Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-31 15:12 +0100
                Re: Suggestion: make sequence and map interfaces more similar Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-04-01 09:59 +0200
                Re: Suggestion: make sequence and map interfaces more similar Tim Golden <mail@timgolden.me.uk> - 2016-04-01 09:27 +0100
                Re: Suggestion: make sequence and map interfaces more similar Steven D'Aprano <steve@pearwood.info> - 2016-04-01 21:38 +1100
                Re: Suggestion: make sequence and map interfaces more similar Marko Rauhamaa <marko@pacujo.net> - 2016-04-01 13:50 +0300
                Re: Suggestion: make sequence and map interfaces more similar Rustom Mody <rustompmody@gmail.com> - 2016-04-01 07:41 -0700
                Re: Suggestion: make sequence and map interfaces more similar Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-04-01 10:04 +0100
                Re: Suggestion: make sequence and map interfaces more similar Marco Sulla <mail.python.org@marco.sulla.e4ward.com> - 2016-03-30 21:35 +0200
                Re: Suggestion: make sequence and map interfaces more similar Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-30 21:31 +0100
            Re: Suggestion: make sequence and map interfaces more similar Manolo Martínez <manolo@austrohungaro.com> - 2016-03-30 12:26 +0200
              Re: Suggestion: make sequence and map interfaces more similar Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-03-30 13:40 +0300
                Re: Suggestion: make sequence and map interfaces more similar Manolo Martínez <manolo@austrohungaro.com> - 2016-03-30 12:50 +0200
                Re: Suggestion: make sequence and map interfaces more similar Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-03-30 14:21 +0300
                Re: Suggestion: make sequence and map interfaces more similar Marko Rauhamaa <marko@pacujo.net> - 2016-03-30 14:44 +0300
                Re: Suggestion: make sequence and map interfaces more similar Manolo Martínez <manolo@austrohungaro.com> - 2016-03-30 14:29 +0200
                Re: Suggestion: make sequence and map interfaces more similar Marko Rauhamaa <marko@pacujo.net> - 2016-03-30 15:55 +0300
                Re: Suggestion: make sequence and map interfaces more similar Manolo Martínez <manolo@austrohungaro.com> - 2016-03-30 15:13 +0200
                Re: Suggestion: make sequence and map interfaces more similar Steven D'Aprano <steve@pearwood.info> - 2016-03-30 23:27 +1100
                Re: Suggestion: make sequence and map interfaces more similar Marko Rauhamaa <marko@pacujo.net> - 2016-03-30 15:48 +0300
                Re: Suggestion: make sequence and map interfaces more similar Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-03-30 17:38 +0300
                Re: Suggestion: make sequence and map interfaces more similar Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-03-30 17:25 +0300
        Re: Suggestion: make sequence and map interfaces more similar Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-03-30 10:55 +0200
        Re: Suggestion: make sequence and map interfaces more similar Random832 <random832@fastmail.com> - 2016-03-30 08:50 -0400
          Re: Suggestion: make sequence and map interfaces more similar Steven D'Aprano <steve@pearwood.info> - 2016-03-31 03:02 +1100
            Re: Suggestion: make sequence and map interfaces more similar Random832 <random832@fastmail.com> - 2016-03-30 12:52 -0400
              Re: Suggestion: make sequence and map interfaces more similar Steven D'Aprano <steve@pearwood.info> - 2016-03-31 13:44 +1100
                Re: Suggestion: make sequence and map interfaces more similar Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-03-31 10:04 +0200
                Re: Suggestion: make sequence and map interfaces more similar Marco Sulla <mail.python.org@marco.sulla.e4ward.com> - 2016-03-31 13:58 +0200
                Re: Suggestion: make sequence and map interfaces more similar Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-31 13:30 +0100
                Re: Suggestion: make sequence and map interfaces more similar Marco Sulla <mail.python.org@marco.sulla.e4ward.com> - 2016-03-31 14:49 +0200
                Re: Suggestion: make sequence and map interfaces more similar Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-31 14:14 +0100
            Re: Suggestion: make sequence and map interfaces more similar Marco Sulla <mail.python.org@marco.sulla.e4ward.com> - 2016-03-30 22:00 +0200
            Re: Suggestion: make sequence and map interfaces more similar Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-30 21:36 +0100
    Re: Suggestion: make sequence and map interfaces more similar Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-30 08:03 +0100

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