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enhancing/wrapping an existing instance of a duck

Basically I have an existing (maybe a rather large and complicated
(existing) instance) that
I want to add new member to.


Hacks/attempts follow:

from math import sqrt

############ try2 ############
duck_obj = [ i*i for i in range(25) ] # OR a large sparse matrix

# I "want" to an a useful property, eg length, and retain the ducks
existing properties.
# I COULD try...
setattr(duck_ob j,"length",lamb da: sqrt(sum(*duck_ obj)))
print duck_obj.length () # returns 70
print duck_obj.length () # returns 71

############ try2 ############
# **BUT** I'd rather encapsulate a the original instance somehow.

# I presume that I could define a class to do this somehow?
duck_obj = [ i*i for i in range(25) ] # OR a LargeSparseMatr ix()

dec = Vec(duck_obj) ???
print dec.length() # returns 70
duck_obj[0]=70+71 # original "large and complicated duck instance"
print dec.length() # returns 71

Any hints on how I need to define Vec so that any kind of duck_obj can
be decorated/wrapped/encapsulated.
Sep 1 '08 #1
0 769

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