Re: Newbie question about text encoding

References	(14 earlier) <87twxw4xlz.fsf@elektro.pacujo.net> <54fba9d4$0$12988$c3e8da3$5496439d@news.astraweb.com> <87y4n8uf9a.fsf@elektro.pacujo.net> <mailman.163.1425800257.21433.python-list@python.org> <87twxvvrjl.fsf@elektro.pacujo.net>
Date	2015-03-08 19:23 +1100
Subject	Re: Newbie question about text encoding
From	Chris Angelico <rosuav@gmail.com>
Newsgroups	comp.lang.python
Message-ID	<mailman.166.1425803025.21433.python-list@python.org> (permalink)

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On Sun, Mar 8, 2015 at 7:09 PM, Marko Rauhamaa <marko@pacujo.net> wrote:
> Chris Angelico <rosuav@gmail.com>:
>
>> Once again, you appear to be surprised that invalid data is failing.
>> Why is this so strange? U+DD00 is not a valid character. It is quite
>> correct to throw this error.
>
> '\udd00' is a valid str object:
>
>    >>> '\udd00'
>    '\udd00'
>    >>> '\udd00'.encode('utf-32')
>    b'\xff\xfe\x00\x00\x00\xdd\x00\x00'
>    >>> '\udd00'.encode('utf-16')
>    b'\xff\xfe\x00\xdd'
>
> I was simply stating that UTF-8 is not a bijection between unicode
> strings and octet strings (even forgetting Python). Enriching Unicode
> with 128 surrogates (U+DC80..U+DCFF) establishes a bijection, but not
> without side effects.

But it's not a valid Unicode string, so a Unicode encoding can't be
expected to cope with it. Mathematically, 0xC0 0x80 would represent
U+0000, and some UTF-8 codecs generate and accept this (in order to
allow U+0000 without ever yielding 0x00), but that doesn't mean that
UTF-8 should allow that byte sequence.

The only reason to craft some kind of Unicode string for any arbitrary
sequence of bytes is the "smuggling" effect used for file name
handling. There is no reason to support invalid Unicode codepoints.

ChrisA

Thread

Newbie question about text encoding pierrick.brihaye@gmail.com - 2015-02-24 02:49 -0800
  Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-02-24 22:09 +1100
  Re: Newbie question about text encoding Dave Angel <davea@davea.name> - 2015-02-24 06:25 -0500
  Re: Newbie question about text encoding Laura Creighton <lac@openend.se> - 2015-02-24 15:55 +0100
  Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-02-25 02:03 +1100
  Re: Newbie question about text encoding Laura Creighton <lac@openend.se> - 2015-02-24 16:06 +0100
    Re: Newbie question about text encoding wxjmfauth@gmail.com - 2015-02-24 08:01 -0800
  Re: Newbie question about text encoding Laura Creighton <lac@openend.se> - 2015-02-24 16:07 +0100
  Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-02-25 02:10 +1100
  Re: Newbie question about text encoding Laura Creighton <lac@openend.se> - 2015-02-24 16:24 +0100
  Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-02-25 02:33 +1100
  Re: Newbie question about text encoding random832@fastmail.us - 2015-02-24 10:38 -0500
  Re: Newbie question about text encoding Laura Creighton <lac@openend.se> - 2015-02-24 17:20 +0100
  Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-02-25 03:24 +1100
  Re: Newbie question about text encoding Dave Angel <davea@davea.name> - 2015-02-24 12:13 -0500
  Re: Newbie question about text encoding Laura Creighton <lac@openend.se> - 2015-02-24 20:45 +0100
    Re: Newbie question about text encoding Marko Rauhamaa <marko@pacujo.net> - 2015-02-25 00:21 +0200
    Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-02-25 12:20 +1100
      Re: Newbie question about text encoding wxjmfauth@gmail.com - 2015-02-25 06:34 -0800
  Re: Newbie question about text encoding Laura Creighton <lac@openend.se> - 2015-02-24 20:57 +0100
    Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-02-25 12:19 +1100
      Re: Newbie question about text encoding Marcos Almeida Azevedo <marcos.al.azevedo@gmail.com> - 2015-02-25 12:54 +0800
  Re: Newbie question about text encoding Dave Angel <davea@davea.name> - 2015-02-24 15:41 -0500
    Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-02-26 04:40 -0800
      Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-02-26 05:15 -0800
      Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-02-27 00:24 +1100
        Re: Newbie question about text encoding Sam Raker <sam.raker@gmail.com> - 2015-02-26 08:45 -0800
          Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-02-26 09:08 -0800
      Re: Newbie question about text encoding Terry Reedy <tjreedy@udel.edu> - 2015-02-26 12:02 -0500
        Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-02-26 09:59 -0800
          Re: Newbie question about text encoding wxjmfauth@gmail.com - 2015-02-26 12:20 -0800
          Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-02-27 09:13 +1100
          Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-02-27 12:05 +1100
            Re: Newbie question about text encoding Dave Angel <davea@davea.name> - 2015-02-26 20:57 -0500
              Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-02-27 16:58 +1100
                Re: Newbie question about text encoding Dave Angel <davea@davea.name> - 2015-02-27 02:30 -0500
                Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-02-27 22:54 +1100
                Re: Newbie question about text encoding Dave Angel <davea@davea.name> - 2015-02-27 09:02 -0500
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-02-28 01:22 +1100
                Re: Newbie question about text encoding alister <alister.nospam.ware@ntlworld.com> - 2015-02-27 16:00 +0000
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-02-28 03:12 +1100
                Re: Newbie question about text encoding alister <alister.nospam.ware@ntlworld.com> - 2015-02-27 16:45 +0000
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-02-28 04:45 +1100
                Re: Newbie question about text encoding alister <alister.nospam.ware@ntlworld.com> - 2015-02-27 22:13 +0000
                Re: Newbie question about text encoding MRAB <python@mrabarnett.plus.com> - 2015-02-27 19:14 +0000
                Re: Newbie question about text encoding alister <alister.nospam.ware@ntlworld.com> - 2015-02-27 22:09 +0000
                Re: Newbie question about text encoding Dave Angel <davea@davea.name> - 2015-02-27 15:52 -0500
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-02-28 08:04 +1100
                Re: Newbie question about text encoding Dave Angel <davea@davea.name> - 2015-02-27 10:24 -0500
                Re: Newbie question about text encoding Grant Edwards <invalid@invalid.invalid> - 2015-02-27 17:46 +0000
                Re: Newbie question about text encoding Grant Edwards <invalid@invalid.invalid> - 2015-02-27 17:47 +0000
            Re: Newbie question about text encoding wxjmfauth@gmail.com - 2015-02-27 01:06 -0800
        Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-02-26 11:59 -0800
        Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-03-03 10:03 -0800
          Re: Newbie question about text encoding wxjmfauth@gmail.com - 2015-03-03 10:36 -0800
            Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-03-03 20:45 -0800
              Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-04 15:54 +1100
                Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-03-03 21:05 -0800
                Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-06 01:06 +1100
                Re: Newbie question about text encoding wxjmfauth@gmail.com - 2015-03-05 06:59 -0800
                Re: Newbie question about text encoding random832@fastmail.us - 2015-03-05 14:59 -0500
                Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-06 09:33 +1100
                Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-03-05 20:53 -0800
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-06 16:20 +1100
                Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-03-06 01:02 -0800
                Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-03-06 01:06 -0800
                Re: Newbie question about text encoding random832@fastmail.us - 2015-03-06 08:33 -0500
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-07 00:39 +1100
                Re: Newbie question about text encoding random832@fastmail.us - 2015-03-06 09:03 -0500
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-07 01:11 +1100
                Re: Newbie question about text encoding random832@fastmail.us - 2015-03-06 09:27 -0500
                Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-07 03:26 +1100
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-06 20:54 +1100
                Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-03-06 02:07 -0800
                Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-07 01:50 +1100
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-07 02:27 +1100
                Re: Newbie question about text encoding wxjmfauth@gmail.com - 2015-03-06 07:37 -0800
                Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-03-06 08:20 -0800
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-07 03:45 +1100
                Re: Newbie question about text encoding wxjmfauth@gmail.com - 2015-03-06 11:41 -0800
                Re: Newbie question about text encoding wxjmfauth@gmail.com - 2015-03-06 11:58 -0800
                Re: Newbie question about text encoding Terry Reedy <tjreedy@udel.edu> - 2015-03-07 01:11 -0500
                Re: Newbie question about text encoding wxjmfauth@gmail.com - 2015-03-06 23:43 -0800
                Re: Newbie question about text encoding wxjmfauth@gmail.com - 2015-03-07 00:55 -0800
                Re: Newbie question about text encoding wxjmfauth@gmail.com - 2015-03-07 01:08 -0800
                Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-03-07 21:25 -0800
                Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-07 22:09 +1100
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-07 22:33 +1100
                Re: Newbie question about text encoding Marko Rauhamaa <marko@pacujo.net> - 2015-03-07 13:53 +0200
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-07 23:02 +1100
                Re: Newbie question about text encoding Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-03-07 14:07 +0000
                Re: Newbie question about text encoding wxjmfauth@gmail.com - 2015-03-07 07:28 -0800
                Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-08 02:40 +1100
                Re: Newbie question about text encoding Marko Rauhamaa <marko@pacujo.net> - 2015-03-07 17:48 +0200
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-08 03:17 +1100
                Re: Newbie question about text encoding Marko Rauhamaa <marko@pacujo.net> - 2015-03-07 18:25 +0200
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-08 03:41 +1100
                Re: Newbie question about text encoding Marko Rauhamaa <marko@pacujo.net> - 2015-03-07 18:54 +0200
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-08 03:58 +1100
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-08 04:00 +1100
                Re: Newbie question about text encoding Marko Rauhamaa <marko@pacujo.net> - 2015-03-07 19:14 +0200
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-08 04:26 +1100
                Re: Newbie question about text encoding Marko Rauhamaa <marko@pacujo.net> - 2015-03-07 19:50 +0200
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-08 04:59 +1100
                Re: Newbie question about text encoding Dan Sommers <dan@tombstonezero.net> - 2015-03-07 18:02 +0000
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-08 05:13 +1100
                Re: Newbie question about text encoding Dan Sommers <dan@tombstonezero.net> - 2015-03-07 18:34 +0000
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-08 05:44 +1100
                Re: Newbie question about text encoding Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-03-07 19:00 +0000
                Re: Newbie question about text encoding Dan Sommers <dan@tombstonezero.net> - 2015-03-07 19:16 +0000
                Re: Newbie question about text encoding Marko Rauhamaa <marko@pacujo.net> - 2015-03-07 21:01 +0200
                Re: Newbie question about text encoding Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-03-07 16:40 +0000
                Re: Newbie question about text encoding Marko Rauhamaa <marko@pacujo.net> - 2015-03-07 18:48 +0200
                Re: Newbie question about text encoding Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-03-07 17:02 +0000
                Re: Newbie question about text encoding Marko Rauhamaa <marko@pacujo.net> - 2015-03-07 19:16 +0200
                Re: Newbie question about text encoding Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-03-07 18:18 +0000
                Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-03-07 21:06 -0800
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-08 03:53 +1100
                Re: Newbie question about text encoding wxjmfauth@gmail.com - 2015-03-07 11:03 -0800
                Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-08 12:45 +1100
                Re: Newbie question about text encoding Marko Rauhamaa <marko@pacujo.net> - 2015-03-08 09:20 +0200
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-08 18:37 +1100
                Re: Newbie question about text encoding Marko Rauhamaa <marko@pacujo.net> - 2015-03-08 10:09 +0200
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-08 19:23 +1100
                Re: Newbie question about text encoding wxjmfauth@gmail.com - 2015-03-08 01:18 -0800
                Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-09 05:25 +1100
                Re: Newbie question about text encoding Marko Rauhamaa <marko@pacujo.net> - 2015-03-08 22:09 +0200
                Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-09 12:43 +1100
                Re: Newbie question about text encoding Ben Finney <ben+python@benfinney.id.au> - 2015-03-09 13:09 +1100
                Re: Newbie question about text encoding Marko Rauhamaa <marko@pacujo.net> - 2015-03-09 08:31 +0200
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-09 13:18 +1100
                Re: Newbie question about text encoding random832@fastmail.us - 2015-03-09 00:27 -0400
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-09 07:55 +1100
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-09 08:13 +1100
                Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-09 17:34 +1100
                Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-09 17:44 +1100
                Re: Newbie question about text encoding wxjmfauth@gmail.com - 2015-03-09 02:08 -0700
                Re: Newbie question about text encoding wxjmfauth@gmail.com - 2015-03-09 07:26 -0700
                Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-03-09 05:28 -0700
                Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-08 19:01 +1100
                Re: Newbie question about text encoding Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-03-07 14:13 +0000
                Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-03-07 23:23 -0800
                Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-09 05:30 +1100
                Re: Newbie question about text encoding Cameron Simpson <cs@zip.com.au> - 2015-03-09 13:09 +1100
                Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-03-08 19:42 -0700
                Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-04 19:16 +1100
          Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-04 05:43 +1100
            Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-03-03 18:53 -0800
          Re: Newbie question about text encoding Terry Reedy <tjreedy@udel.edu> - 2015-03-03 18:30 -0500
          Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-04 13:54 +1100
            Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-03-04 14:02 +1100
            Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-03-03 20:05 -0800
              Re: Newbie question about text encoding Rustom Mody <rustompmody@gmail.com> - 2015-03-03 20:16 -0800
              Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-04 19:14 +1100
                Re: Newbie question about text encoding wxjmfauth@gmail.com - 2015-03-04 02:16 -0800
      Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-02-27 04:29 +1100
        Re: Newbie question about text encoding Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-02-27 10:09 +1100
          Re: Newbie question about text encoding Chris Angelico <rosuav@gmail.com> - 2015-02-27 10:23 +1100

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