[Tutor] Class vs. Static Methods

Chuck Allison chuck at freshsources.com
Thu Jun 23 02:18:10 CEST 2005

Hello Kent,

This is the killer example I've been looking for. Now I understand.
Sorry I've been so dense. This is way cool. Thanks.

Wednesday, June 22, 2005, 4:39:38 AM, you wrote:

KJ> Not sure why you think you have to write a new classmethod for
KJ> each shape. Suppose you want to maintain creation counts for each
KJ> class. Here is one way to do it using classmethods:

KJ> class Shape(object):
KJ>   _count = 0    # Default for classes with no instances (cls.count() never called)
KJ>   @classmethod
KJ>   def count(cls):
KJ>     try:
KJ>       cls._count += 1
KJ>     except AttributeError:
KJ>       cls._count = 1
KJ>   @classmethod
KJ>   def showCount(cls):
KJ>     print 'Class %s has count = %s' % (cls.__name__, cls._count)
KJ>   def __init__(self):
KJ>     self.count()

KJ> class Point(Shape): pass

KJ> class Line(Shape): pass

KJ> p, p2, p = Point(), Point(), Point()
KJ> Point.showCount()

KJ> Line.showCount()
KJ> l = Line()
KJ> Line.showCount()

KJ> ### prints
KJ> Class Point has count = 3
KJ> Class Line has count = 0
KJ> Class Line has count = 1

KJ> Kent

Best regards,

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