Ron Phillips wrote:
> short version: I need a way to get max and min E and N out of
> [(E0,N0),(E1,N1)...(En,Nn)] without reordering the list
not sure if your coordinates are strings like 'E0' or if that is a placeholder
for an int. If they
are ints you can use
minE = min(e for e,n in coordList)
If they are strings you have to convert
minE = min(int(e[1:]) for e,n in coordList)
etc
For Python < 2.4 you need another set of [ ] e.g. min([e for e,n in coordList])
> long version:
>
> I would like a list of geographic coordinates (Easting, Northing) to
> maintain a "bounding box"
> [(minEasting,minNorthing),(maxEasting,maxNorthing)] attribute.
>
> I did it like this:
>
> class geoCoordinateList(UserList):
> def __init__(self):
> UserList.__init__(self)
> self.boundingBox = geoBox(minEN=geoCoordinate(),
> maxEN=geoCoordinate())
> def append(self, geoCoord):
> self.extend([geoCoord])
> self.boundingBox.challenge(geoCoord)#bumps the max and min if
> necessary
> but I'd have to override almost all the UserList methods, unless there's
> a way to call boundingBox.challenge() on any change to the list.
If you don't need too much list functionality it might be easier to wrap a list
and delegate the
things you need:
class geoCoordinateList(object):
def __init__(self):
self.list = list()
self.boundingBox = geoBox(minEN=geoCoordinate(),
maxEN=geoCoordinate())
def append(self, geoCoord):
self.list.append(geoCoord) # No need for extend() here...
self.boundingBox.challenge(geoCoord)#bumps the max and min if necessary
I think you will want at least __getitem__() and __len__() as well.
Kent
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