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Date: Thu, 04 Jul 2013 16:10:56 +0100
From: MRAB <python@mrabarnett.plus.com>
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To: python-list@python.org
Subject: Re: UnicodeDecodeError: 'utf-8' codec can't decode byte 0xb6 in position 0: invalid start byte
References: <kr3c7k$tjs$2@news.grnet.gr> <n3tfaa-eqh.ln1@satorlaser.homedns.org> <kr3jai$jn0$4@news.grnet.gr> <mailman.4219.1372935984.3114.python-list@python.org> <kr3mnq$jn0$6@news.grnet.gr> <mailman.4222.1372939645.3114.python-list@python.org> <kr3qss$9h4$1@news.grnet.gr> <mailman.4229.1372944863.3114.python-list@python.org> <51D57ADB.3050202@superhost.gr>
In-Reply-To: <51D57ADB.3050202@superhost.gr>
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Xref: csiph.com comp.lang.python:49872

On 04/07/2013 14:38, Νίκος Γκρ33κ wrote:
> Στις 4/7/2013 4:34 μμ, ο/η MRAB έγραψε:
>> On 04/07/2013 13:47, Νίκος wrote:
>>> Στις 4/7/2013 3:07 μμ, ο/η MRAB έγραψε:
>>>> On 04/07/2013 12:36, Νίκος wrote:
>>>>> Στις 4/7/2013 2:06 μμ, ο/η MRAB έγραψε:
>>>>>> On 04/07/2013 11:38, Νίκος wrote:
>>>>>>> Στις 4/7/2013 12:50 μμ, ο/η Ulrich Eckhardt έγραψε:
>>>>>>>> Am 04.07.2013 10:37, schrieb Νίκος:
>>>>>>>>> I just started to have this error without changing nothing
>>>>>>>>
>>>>>>>> Well, undo the nothing that you didn't change. ;)
>>>>>>>>
>>>>>>>>> UnicodeDecodeError: 'utf-8' codec can't decode byte 0xb6 in
>>>>>>>>> position 0:
>>>>>>>>> invalid start byte
>>>>>>>>> [Thu Jul 04 11:35:14 2013] [error] [client 108.162.229.97]
>>>>>>>>> Premature
>>>>>>>>> end
>>>>>>>>> of script headers: metrites.py
>>>>>>>>>
>>>>>>>>> Why cant it decode the starting byte? what starting byte is that?
>>>>>>>>
>>>>>>>> It's the 0xb6 but it's expecting the starting byte of a UTF-8
>>>>>>>> sequence.
>>>>>>>> Please do some research on UTF-8, that should clear it up. You could
>>>>>>>> also search for common causes of that error.
>>>>>>>
>>>>>>> So you are also suggesting that what gesthostbyaddr() returns is not
>>>>>>> utf-8 encoded too?
>>>>>>>
>>>>>>> What character is 0xb6 anyways?
>>>>>>>
>>>>>> Well, it's from a bytestring, so you'll have to specify what encoding
>>>>>> you're using! (It clearly isn't UTF-8.)
>>>>>>
>>>>>> If it's ISO-8859-7 (what you've previously referred to as
>>>>>> "greek-iso"),
>>>>>> then:
>>>>>>
>>>>>>  >>> import unicodedata
>>>>>>  >>> unicodedata.name(b"\xb6".decode("ISO-8859-7"))
>>>>>> 'GREEK CAPITAL LETTER ALPHA WITH TONOS'
>>>>>>
>>>>>> You'll need to find out where that bytestring is coming from.
>>>>>
>>>>> Right.
>>>>> But nowhere in my script(metrites.py) i use an 'Ά' so i really have no
>>>>> clue where this is coming from.
>>>>>
>>>>> And you are right if it was a byte came from an utf-8 encoding scheme
>>>>> then it would be automatically decoded.
>>>>>
>>>>> The only thing i can say for use is that this problem a[[ear only
>>>>> when i
>>>>> cloudflare my domain "superhost.gr"
>>>>>
>>>>> If i un-cloudlflare it it cease to display errors.
>>>>>
>>>>> Can you tell me hpw to write the following properly:
>>>>>
>>>>> host = socket.gethostbyaddr( os.environ['REMOTE_ADDR'] )[0] or
>>>>> 'UnResolved'
>>>>>
>>>>> so even if the function fails "unresolved" to be returned back?
>>>>> Somehow i need to capture the error.
>>>>>
>>>>> Or it dosnt have to do it the or operand will be returned?
>>>>>
>>>> If gethostbyaddr fails, it raises socket.gaierror, (which, from Python
>>>> 3.3 onwards, is a subclass of OSError), so try catching that, setting
>>>> 'host' to 'UnResolved' if it's raised.
>>>>
>>>> Also, try printing out ascii(os.environ['REMOTE_ADDR']).
>>>>
>>>
>>> I have followed your suggestion by trying this:
>>>
>>> try:
>>>     host = socket.gethostbyaddr( os.environ['REMOTE_ADDR'] )[0]
>>> except socket.gaierror:
>>>     host = "UnResolved"
>>>
>>> and then re-cloudlflared "superhost.gr" domain
>>>
>>> http://superhost.gr/ gives internal server error.
>>>
>> Try catching OSError instead. (As I said, from Python 3.3,
>> socket.gaierror is a subclass of it.)
>>
>
> At least CloudFlare doesn't give me issues:
>
> if i try this:
>
> try:
> 	host = os.environ['REMOTE_ADDR'][0]
> except socket.gaierror:
> 	host = "UnResolved"
>
It's pointless trying to catch a socket exception here because you're
not using a socket, you're just getting a string from an environment
variable.

> then i get no errors and a valid ip back
>
> but the above fails.
>
> I don't know how to catch the exception with OSError.
>
> i know only this two:
>
> except socket.gaierror:
> except socket.herror
>
> both fail.
>
What do you mean "I don't know how to catch the exception with
OSError"? You've tried "except socket.gaierror" and "except
socket.herror", well just write "except OSError" instead!