Handling 3 operands in an expression without raising an exception

[Antoon Pardon]

Op 26-09-13 12:18, Νίκος schreef:
> Στις 26/9/2013 1:12 μμ, ο/η Antoon Pardon έγραψε:
>> Op 26-09-13 11:56, Νίκος schreef:
>>> Στις 26/9/2013 11:55 πμ, ο/η Nobody έγραψε:
>>>> On Thu, 26 Sep 2013 10:26:48 +0300, Νίκος wrote:
>>>>
>>>>> How can i wrote the two following lines so for NOT to throw out
>>>>> KeyErrors when a key is missing?
>>>>>
>>>>> city = gi.time_zone_by_addr( os.environ['HTTP_CF_CONNECTING_IP'] ) or
>>>>> gi.time_zone_by_addr( os.environ['REMOTE_ADDR'] ) or
>>>>> "Άγνωστη Πόλη"
>>>>
>>>> tz = None
>>>> ip = os.environ.get('HTTP_CF_CONNECTING_IP')
>>>> if ip:
>>>>     tz = gi.time_zone_by_addr(ip)
>>>> if not tz:
>>>>     ip = os.environ.get('REMOTE_ADDR')
>>>>     if ip:
>>>>       tz = gi.time_zone_by_addr(ip)
>>>> if not tz:
>>>>     tz = "ÎγνÏÏÏη Î Ïλη"
>>>>
>>>> Likewise for the hostname.
>>>>
>>>
>>> Its logic is simple and straightforward but too many lines:
>>>
>>> host = socket.gethostbyaddr( os.environ.get('HTTP_CF_CONNECTING_IP') or
>>> os.environ.get('REMOTE_ADDR') or  "Άγνωστη Προέλευση" )
>>>
>>> this is much better in my opinion and straighforward also and more clear
>>> to read:
>>
>> No it is not and you prove that in the very next line.
>>
>>> it doens't work though:
>>
>> If it doesn't do what you think it should do then it is not straight
>> forward or clear, at least not to you.
> 
> It is far better than the ifs, even easier to read, i was just missing a
> [0] at the end.
> 
> host = socket.gethostbyaddr( os.environ.get('HTTP_CF_CONNECTING_IP') or
> os.environ.get('REMOTE_ADDR') or  "Άγνωστη Προέλευση" )[0]

No it is not. Your purpose was to have a line that wouldn't throw an
exception even if some environ variables were not available. That
means it shouldn't throw an exception when I execute the code. Guess
what happens:

>>> socket.gethostbyaddr( os.environ.get('HTTP_CF_CONNECTING_IP') or
os.environ.get('REMOTE_ADDR') or  "Άγνωστη Προέλευση" )[0]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
socket.gaierror: [Errno -2] Name or service not known

You are just illustrating your lack of basic understaning.

-- 
Antoon Pardon