At Friday 25/8/2006 00:36, [EMAIL PROTECTED] wrote:
# This is what I have in mind:
class Item(object):
def __add__(self, other):
return Add(self, other)
And this works fine... why make thinks complicated?
# Now, I am going absolutely crazy with this idea
# and using it in a big way. So I'm looking at
# automating the process. As a first step,
# I thought maybe this would work:
class Item(object):
pass
class Add(Item):
def __init__(self, a, b=None):
print self, a, b
self.a = a
self.b = b
Item.__add__ = Add
This doesn't make sense... __add__ should be a method, not a class...
x = Item()
y = Item()
print x, y
c = x+y
# This time, the Add constructor gets only the first two arguments:
"self" and "y".
# So, what happened to "x" ? Is this some kind of property voodoo going
on ?
x+y get translated to x.__add__(y)
x.__add__ is Add (the class), so Python calls Add, which means using
it as a constructor with y as the (only) argument.
So you see in the __init__ method: self=a new instance of Add, a=y,
b=None (default, as only one argument was provided).
If you really want to "inject" __add__ into the Item class, you could
use a factory:
def AddFactory(a,b):
return Add(a,b)
Item.__add__ = AddFactory
(but as you've said yourself, that's a bit crazy...)
Gabriel Genellina
Softlab SRL
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