umlauts

[Diez B. Roggisch]

StarWing schrieb:
> On 10月18日, 上午12时50分, "Diez B. Roggisch" <de... at nospam.web.de> wrote:
>> StarWing schrieb:
>>
>>
>>
>>> On 10月17日, 下午9时54分, Arian Kuschki <arian.kusc... at googlemail.com>
>>> wrote:
>>>> Hi all
>>>> this has been bugging me for a long time and I do not seem to be able to
>>>> understand what to do. I always have problems when dealing input text that
>>>> contains umlauts. Consider the following:
>>>> In [1]: import urllib
>>>> In [2]: f = urllib.urlopen("http://www.google.de/ig/api?weather=Muenchen")
>>>> In [3]: xml = f.read()
>>>> In [4]: f.close()
>>>> In [5]: print xml
>>>> ------> print(xml)
>>>> <?xml version="1.0"?><xml_api_reply version="1"><weather module_id="0"
>>>> tab_id="0" mobile_row="0" mobile_zipped="1" row="0" section="0"><forecast_information><cit
>>>> y data="Munich, BY"/><postal_code data="Muenchen"/><latitude_e6
>>>> data=""/><longitude_e6 data=""/><forecast_date
>>>> data="2009-10-17"/><current_date_time data="2009-10
>>>> -17 14:20:00 +0000"/><unit_system
>>>> data="SI"/></forecast_information><current_conditions><condition data="Meistens
>>>> bew kt"/><temp_f data="43"/><temp_c data="6"/><h
>>>> umidity data="Feuchtigkeit: 87 %"/><icon
>>>> data="/ig/images/weather/mostly_cloudy.gif"/><wind_condition data="Wind: W mit
>>>> Windgeschwindigkeiten von 13 km/h"/></curr
>>>> ent_conditions><forecast_conditions><day_of_week data="Sa."/><low
>>>> data="1"/><high data="7"/><icon
>>>> data="/ig/images/weather/chance_of_rain.gif"/><condition data="V
>>>> ereinzelt Regen"/></forecast_conditions><forecast_conditions><day_of_week
>>>> data="So."/><low data="-1"/><high data="8"/><icon
>>>> data="/ig/images/weather/chance_of_sno
>>>> w.gif"/><condition data="Vereinzelt
>>>> Schnee"/></forecast_conditions><forecast_conditions><day_of_week
>>>> data="Mo."/><low data="-4"/><high data="8"/><icon data="/ig/i
>>>> mages/weather/mostly_sunny.gif"/><condition data="Teils
>>>> sonnig"/></forecast_conditions><forecast_conditions><day_of_week
>>>> data="Di."/><low data="0"/><high data="8"
>>>> /><icon data="/ig/images/weather/sunny.gif"/><condition
>>>> data="Klar"/></forecast_conditions></weather></xml_api_reply>
>>>> As you can see the umlauts in the XML are not displayed properly. When I want
>>>> to process this text (for example with xml.sax), I get error messages because
>>>> the parses can't read this.
>>>> I've tried to read up on this and there is a lot of information on the web, but
>>>> nothing seems to work for me. For example setting the coding to UTF like this:
>>>> # -*- coding: utf-8 -*- or using the decode() string method.
>>>> I always have this kind of problem when input contains umlauts, not just in
>>>> this case. My locale (on Ubuntu) is en_GB.UTF-8.
>>>> Cheers
>>>> Arian
>>> try this?
>>> # vim: set fencoding=utf-8:
>>> import urllib
>>> import xml.sax as sax, xml.sax.handler as handler
>>> f = urllib.urlopen("http://www.google.de/ig/api?weather=Muenchen")
>>> xml = f.read()
>>> xml = xml.decode("cp1252")
>>> f.close()
>>> class my_handler(handler.ContentHandler):
>>>     def startElement(self, name, attrs):
>>>         print "begin:", name, attrs
>>>     def endElement(self, name):
>>>         print "end:", name
>>> sax.parseString(xml, my_handler())
>> This is wrong. XML is a *byte*-based format, which explicitly states
>> encodings. So decoding a byte-string to a unicode-object and then
>> passing it to a parser is not working in the very moment you have data that
>>
>>   - is outside your default-system-encoding (ususally ascii)
>>   - the system-encoding and the declared decoding differ
>>
>> Besides, I don't see where the whole SAX-stuff is supposed to do
>> anything the direct print  and the decode() don't do - smells like
>> cargo-cult to me.
>>
>> Diez
> 
> yes, XML is a *byte*-based format, and so as utf-8 and code-page
> (cp936, cp1252, etc.). so usually XML will sign its coding at head.
> but this didn't work now.
> 
> in Python2.6, sys.getdefaultcoding() return 'ascii', and I can't use
> sys.setdefaultcoding(), and f.read() return a str. so it must be a
> undecoded, byte-base format (i.e. raw XML data). so use the right code-
> page to decode it is safe.(notice the webpage is google.de).
> 
> in Python3.1, read() returns a bytes object. so we *must* decode it,
> nor we can't pass it into a parser.

You didn't get my point. A XML-parser only *takes* a byte-string. 
Decoding is it's business. So your above last sentence is wrong.

Because regardless of the python-version, if you feed the parser a 
unicode-object, python will first encode that to a byte-string, possibly 
giving a UnicodeError (maybe this automated conversion has gone in Py3K, 
but then you get a type-error instead).

So to make the above work (if one wants to parse the xml), the proper 
thing to do would be

   xml = xml.decode("cp1252").encode("utf-8")

and then feed that. Of course the really good thing would be to fix the 
webpage, but that's beyond our capabilities I fear...

Diez