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Groups > comp.lang.python > #53886

Re: Chardet, file, ... and the Flexible String Representation

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On Mon, Sep 9, 2013, at 15:03, Ian Kelly wrote:
> Do you mean that it breaks when overwriting Python string object buffers,
> or when overwriting arbitrary C strings either received from C code or
> created with create_unicode_buffer?
> 
> If the former, I think that is to be expected since ctypes ultimately
> can't
> know what is the actual type of the pointer it was handed -- much as in
> C,
> that's up to the programmer to get right. I also think it's very bad
> practice to be overwriting those anyway, since Python strings are
> supposed
> to be immutable.
> 
> If the latter, that sounds like a bug in ctypes to me.

I was talking about writing to the buffer object from python, i.e. with
slice assignment.
>>> s = 'Test \U00010000'
>>> len(s)
6
>>> buf = create_unicode_buffer(32)
>>> buf[:6] = s
TypeError: one character unicode string expected
>>> buf[:7] = s
ValueError: Can only assign sequence of same size
>>> buf[:7] = 'Test \ud800\udc00'
>>> buf[:7]
'Test \U00010000' # len = 6

Assigning with .value works, however, which may be a viable workaround
for most situations. The "one character unicode string expected" message
is a bit cryptic.

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Chardet, file, ... and the Flexible String Representation wxjmfauth@gmail.com - 2013-09-06 02:11 -0700
  Re: Chardet, file, ... and the Flexible String Representation Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-09-06 10:57 +0000
  Re: Chardet, file, ... and the Flexible String Representation Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-09-06 13:10 +0200
  Re: Chardet, file, ... and the Flexible String Representation Ned Batchelder <ned@nedbatchelder.com> - 2013-09-06 07:02 -0400
  Re: Chardet, file, ... and the Flexible String Representation Piet van Oostrum <piet@vanoostrum.org> - 2013-09-06 11:46 -0400
    Re: Chardet, file, ... and the Flexible String Representation Chris Angelico <rosuav@gmail.com> - 2013-09-07 02:04 +1000
    Re: Chardet, file, ... and the Flexible String Representation random832@fastmail.us - 2013-09-06 12:59 -0400
    Re: Chardet, file, ... and the Flexible String Representation Chris Angelico <rosuav@gmail.com> - 2013-09-07 03:04 +1000
    Re: Chardet, file, ... and the Flexible String Representation wxjmfauth@gmail.com - 2013-09-09 07:28 -0700
      Re: Chardet, file, ... and the Flexible String Representation Ned Batchelder <ned@nedbatchelder.com> - 2013-09-09 12:38 -0400
      Re: Chardet, file, ... and the Flexible String Representation Michael Torrie <torriem@gmail.com> - 2013-09-09 11:05 -0600
        Re: Chardet, file, ... and the Flexible String Representation Steven D'Aprano <steve@pearwood.info> - 2013-09-10 04:58 +0000
      Re: Chardet, file, ... and the Flexible String Representation Terry Reedy <tjreedy@udel.edu> - 2013-09-09 16:47 -0400
      Re: Chardet, file, ... and the Flexible String Representation random832@fastmail.us - 2013-09-10 11:36 -0400
    Re: Chardet, file, ... and the Flexible String Representation random832@fastmail.us - 2013-09-09 14:34 -0400
    Re: Chardet, file, ... and the Flexible String Representation Ian Kelly <ian.g.kelly@gmail.com> - 2013-09-09 13:03 -0600
    Re: Chardet, file, ... and the Flexible String Representation random832@fastmail.us - 2013-09-09 15:27 -0400
    Re: Chardet, file, ... and the Flexible String Representation Serhiy Storchaka <storchaka@gmail.com> - 2013-09-12 00:11 +0300

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