George Sakkis wrote:
> Hi Josiah,
>
>> Hello. I am very new to Python, and have been unable to figure out how
>> to check if a variable exists or not. In the following code I have made
>> a kludge that works, but I think that it would be clearer to check if
>> closest exists and not have to initialize it in the first place. How is
>> that check done?
>>
>> The following code finds the closest place to a position and rejects
>> places that are too far away.
>>
>> dist = 1e9
>> closest = -1
>>
>> for n,p in galaxy.places.iteritems():
>> dif = p.pos - pos
>> len = dif.len()
>> if len < dist and len < 10.0/self.zoom:
>> dist = len
>> closest = p
>>
>> if closest != -1:
>> self.sel = [closest.name]
>
> I would write it like this:
>
> def setClosest(self, pos, galaxy):
> minDist, closestPlace = min([((place.pos-pos).len(), place)
> for place in galaxy.places.itervalues()])
> if minDist < 10.0/self.zoom:
> self.sel = [closestPlace.name]
> else:
> raise RuntimeError("No place close enough")
A galaxy can be pretty big and contain a lot of places ;) You'll easily run
out of memory, if you try to build a list of (dist, place) tuples. Better
use the generator syntax (requires python 2.4):
minDist, closestPlace = min(((place.pos-pos).len(), place)
for place in galaxy.places.itervalues())
--
Benjamin Niemann
Email: pink at odahoda dot de
WWW: http://www.odahoda.de/
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