Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!gegeweb.org!de-l.enfer-du-nord.net!feeder2.enfer-du-nord.net!feeder.news-service.com!newsfeed.xs4all.nl!newsfeed5.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
Date: Thu, 12 May 2011 03:31:18 +0100
From: MRAB <python@mrabarnett.plus.com>
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.9.2.17) Gecko/20110414 Thunderbird/3.1.10
MIME-Version: 1.0
To: python-list@python.org
Subject: Re: unicode by default
References: <OkDyp.2983$M61.450@newsfe07.iad>	<mailman.1433.1305151801.9059.python-list@python.org>	<vpEyp.981$dL5.736@newsfe08.iad>	<mailman.1435.1305157329.9059.python-list@python.org> <KDGyp.180$0t1.7@newsfe04.iad>
In-Reply-To: <KDGyp.180$0t1.7@newsfe04.iad>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: list
Reply-To: python-list@python.org
Newsgroups: comp.lang.python
Message-ID: <mailman.1439.1305167541.9059.python-list@python.org>
Lines: 55
NNTP-Posting-Host: 82.94.164.166
Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:5182

On 12/05/2011 02:22, harrismh777 wrote:
> John Machin wrote:
>> (1) You cannot work without using bytes sequences. Files are byte
>> sequences. Web communication is in bytes. You need to (know / assume / be
>> able to extract / guess) the input encoding. You need to encode your
>> output using an encoding that is expected by the consumer (or use an
>> output method that will do it for you).
>>
>> (2) You don't need to use bytes to specify a Unicode code point. Just use
>> an escape sequence e.g. "\u0404" is a Cyrillic character.
>>
>
> Thanks John. In reverse order, I understand point (2). I'm less clear on
> point (1).
>
> If I generate a string of characters that I presume to be ascii/utf-8
> (no \u0404 type characters) and write them to a file (stdout) how does
> default encoding affect that file.by default..? I'm not seeing that
> there is anything unusual going on... If I open the file with vi? If I
> open the file with gedit? emacs?
>
> ....
>
> Another question... in mail I'm receiving many small blocks that look
> like sprites with four small hex codes, scattered about the mail...
> mostly punctuation, maybe? ... guessing, are these unicode code points,
> and if so what is the best way to 'guess' the encoding? ... is it coded
> in the stream somewhere...protocol?
>
You need to understand the difference between characters and bytes.

A string contains characters, a file contains bytes.

The encoding specifies how a character is represented as bytes.

For example:

     In the Latin-1 encoding, the character "Ł" is represented by the 
byte 0xA3.

     In the UTF-8 encoding, the character "Ł" is represented by the byte 
sequence 0xC2 0xA3.

     In the ASCII encoding, the character "Ł" can't be represented at all.

The advantage of UTF-8 is that it can represent _all_ Unicode
characters (codepoints, actually) as byte sequences, and all those in
the ASCII range are represented by the same single bytes which the
original ASCII system used. Use the UTF-8 encoding unless you have to
use a different one.

A file contains only bytes, a socket handles only bytes. Which encoding
you should use for characters is down to protocol. A system such as
email, which can handle different encodings, should have a way of
specifying the encoding, and perhaps also a default encoding.