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To: python-list@python.org
From: Dave Angel <davea@davea.name>
Subject: Re: Handling 3 operands in an expression without raising an exception
Date: Sun, 29 Sep 2013 10:57:30 +0000 (UTC)
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On 29/9/2013 06:17, Νίκος wrote:

> Στις 29/9/2013 12:50 μμ, ο/η Dave Angel έγραψε:
>> ipval = ( os.environ.get('HTTP_CF_CONNECTING_IP') or
>> os.environ.get('REMOTE_ADDR', "Cannot Resolve") )
>> try:
>> 	gi = pygeoip.GeoIP('/usr/local/share/GeoIPCity.dat')
>> 	city = gi.time_zone_by_addr( ipval )
>> 	host = socket.gethostbyaddr( ipval ) [0]
>> except socket.gaierror as e:
>> 	gi,city,host=globals().get("gi", "who knows"), globals().get("city",
>> "Άγνωστη Πόλη"), globals().get("host", "Άγνωστη
>> Προέλευση")
>
> Hello Dave,
>
> By looking at your code i think that you are tellign the progrma to try 
> to gri don't know what the function globals() is supposed to do

Try help(globals()) at the interpreter prompt.  

Help on built-in function globals in module builtins:

globals(...)
    globals() -> dictionary
    
    Return the dictionary containing the current scope's global variables.

So once you have a dictionary, you can use get() to fetch values which
might or not be present, and supply the default in case they aren't.

>
> but i was thinking more of:
>
> ipval = ( os.environ.get('HTTP_CF_CONNECTING_IP') or
> os.environ.get('REMOTE_ADDR', "Cannot Resolve") )
> try:
> 	city = gi.time_zone_by_addr( ipval )
> 	host = socket.gethostbyaddr( ipval ) [0]
> except socket.gaierror as e:
> 	# We need something here to identify which one of the 2 above variables 
> or even both of them went wrong, and then assign the appropriate value 
> to each one of them but i don't know how to write it.
>
> Is there a function that can tell us which variable failed to be 
> assigned a value that we can use in order to decide to which variable we 
> will
> 	

I showed you the only 3 ways I know of, and none of them is as readable
as just setting the defaults in the standard way.

I only showed you those in order to show you how unreadable it would be.

-- 
DaveA