On 01/25/2013 03:14 PM, Arnaud Delobelle wrote:
I've got a seemingly simple problem, but for which I cannot find a
simple solution.
I have a set of objects (say S) containing an object which is equal to
a given object (say x). So
x in S
is true. So there is an object y in S which is equal to x. My
problem is how to retrieve y, without going through the whole set.
Here is a simple illustration with tuples (my actual scenario is not
with tuples but with a custom class):
y = (1, 2, 3) # This is the 'hidden object'
S = set([y] + range(10000))
x = (1, 2, 3)
x in S
True
x is y
False
I haven't found y. It's a very simple problem, and this is the
simplest solution I can think of:
class FindEqual(object):
def __init__(self, obj):
self.obj = obj
def __hash__(self):
return hash(self.obj)
def __eq__(self, other):
equal = self.obj == other
if equal:
self.lastequal = other
return equal
yfinder = FindEqual(x)
yfinder in S
True
yfinder.lastequal is y
True
I've found y! I'm not happy with this as it really is a trick. Is
there a cleaner solution?
I don't know if there is a cleaner solution, and I quite like yours.
Can you tell us, though, why you have to have y if x == y? Is there
some subtle difference between the two equal objects?
~Ethan~
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