On 8/20/2010 11:45 AM, Gregory, Matthew wrote:
Hi all,
I often struggle with object design and inheritance. I'd like opinions on how
best to design a Point class to be used in multiple circumstances.
I typically deal with geographic (either 2D or 3D) data, yet there are
occasions when I need n-dimensional points as well. My thought was to create a
superclass which was an n-dimensional point and then subclass that to 2- and
3-dimensional cases. The rub to this is that in the n-dimensional case, it
probably makes most sense to store the actual coordinates as a list whereas
with the 2- and 3-D cases, I would want 'named' variables, such as x, y, z.
Here's a (very rough) first cut at the constructor and a generic distance
function for the n-dimensional case:
class PointND(object):
def __init__(self, a_list):
self.a_list = a_list[:]
def distance(self, right):
assert(len(self.coord) == len(right))
squared_diffs = [(i-j)*(i-j) for (i,j) in zip(self.coord, right)]
return math.sqrt(sum(squared_diffs))
But how can I subclass this in such a way to be able to:
1) Have named variables in the 2- and 3-D cases
2) Be able to initialize with separate passed values, e.g. 'p = Point2D(3.0,
5.0)' rather than passing in a list
One class fits all:
class PointND(list):
def __init__(self, *a_list):
super(PointND, self).__init__(a_list)
if len(self)<= 2:
self.x = self[0]
if len(self) == 2:
self.y = self[1]
--
Bob Gailer
919-636-4239
Chapel Hill NC
_______________________________________________
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
