Re: a little parsing challenge ☺

[Benjamin Kaplan]

On Mon, Jul 18, 2011 at 7:07 PM, Billy Mays <noway at nohow.com> wrote:
>
> On 7/18/2011 7:56 PM, Steven D'Aprano wrote:
>>
>> Billy Mays wrote:
>>
>>> On 07/17/2011 03:47 AM, Xah Lee wrote:
>>>>
>>>> 2011-07-16
>>>
>>> I gave it a shot.  It doesn't do any of the Unicode delims, because
>>> let's face it, Unicode is for goobers.
>>
>> Goobers... that would be one of those new-fangled slang terms that the young
>> kids today use to mean its opposite, like "bad", "wicked" and "sick",
>> correct?
>>
>> I mention it only because some people might mistakenly interpret your words
>> as a childish and feeble insult against the 98% of the world who want or
>> need more than the 127 characters of ASCII, rather than understand you
>> meant it as a sign of the utmost respect for the richness and diversity of
>> human beings and their languages, cultures, maths and sciences.
>>
>>
>
> TL;DR version: international character sets are a problem, and Unicode is not the answer to that problem).
>
> As long as I have used python (which I admit has only been 3 years) Unicode has never appeared to be implemented correctly.  I'm probably repeating old arguments here, but whatever.
>
> Unicode is a mess.  When someone says ASCII, you know that they can only mean characters 0-127.  When someone says Unicode, do the mean real Unicode (and is it 2 byte or 4 byte?) or UTF-32 or UTF-16 or UTF-8? When using the 'u' datatype with the array module, the docs don't even tell you if its 2 bytes wide or 4 bytes.  Which is it?  I'm sure that all the of these can be figured out, but the problem is now I have to ask every one of these questions whenever I want to use strings.
>

It doesn't matter. When you use the unicode data type in Python, you
get to treat it as a sequence of characters, not a sequence of bytes.
The fact that it's stored internally as UCS-2 or UCS-4 is irrelevant.

>
> Secondly, Python doesn't do Unicode exception handling correctly. (but I suspect that its a broader problem with languages) A good example of this is with UTF-8 where there are invalid code points ( such as 0xC0, 0xC1, 0xF5, 0xF6, 0xF7, 0xF8, ..., 0xFF, but you already knew that, as well as everyone else who wants to use strings for some reason).
>

A Unicode code point is of the form U+XXXX. 0xC0 is not a Unicode code
point, it is a byte. It happens to be an invalid byte using the UTF-8
byte encoding (which is not Unicode, it's a byte string). The Unicode
code point U+00C0 is perfectly valid- it's a LATIN CAPITAL LETTER A
WITH GRAVE.

>
> When embedding Python in a long running application where user input is received, it is very easy to make mistake which bring down the whole program.  If any user string isn't properly try/excepted, a user could craft a malformed string which a UTF-8 decoder would choke on.  Using ASCII (or whatever 8 bit encoding) doesn't have these problems since all codepoints are valid.
>

UTF-8 != Unicode. UTF-8 is one of several byte encodings capable of
representing every character in the Unicode spec, but it is not
Unicode. If you have a Unicode string, it is not a sequence of byes,
it is a sequence of characters. If you want a sequence of bytes, use a
byte string. If you are attempting to interpret a sequence of bytes as
a sequence of text, you're doing it wrong. There's a reason we have
both text and binary modes for opening files- yes, there is a
difference between them.

> Another (this must have been a good laugh amongst the UniDevs) 'feature' of unicode is the zero width space (UTF-8 code point 0xE2 0x80 0x8B). Any string can masquerade as any other string by placing  few of these in a string.  Any word filters you might have are now defeated by some cheesy Unicode nonsense character.  Can you just just check for these characters and strip them out?  Yes.  Should you have to?  I would say no.
>
> Does it get better?  Of course! international character sets used for domain name encoding use yet a different scheme (Punycode).  Are the following two domain names the same: tést.com , xn--tst-bma.com ?  Who knows!
>
> I suppose I can gloss over the pains of using Unicode in C with every string needing to be an LPS since 0x00 is now a valid code point in UTF-8 (0x0000 for 2 byte Unicode) or suffer the O(n) look up time to do strlen or concatenation operations.
>

That is using UTF-8 in C. Which, again, is not the same thing as Unicode.

> Can it get even better?  Yep.  We also now need to have a Byte order Mark (BOM) to determine the endianness of our characters.  Are they little endian or big endian?  (or perhaps one of the two possible middle endian encodings?)  Who knows?  String processing with unicode is unpleasant to say the least.  I suppose that's what we get when we things are designed by committee.
>

And that is UTF-16 and UTF-32. Again, those are byte encodings. They
are not Unicode. When you use a library capable of handling Unicode,
you never see those- you just have a string with characters in it.

> But Hey!  The great thing about standards is that there are so many to choose from.
>
> --
> Bill
>
>
>
>
>
>
> --
> http://mail.python.org/mailman/listinfo/python-list