I have some code which does a lot of "in" on lists containing objects
with no __eq__ defined.
It all goes fast until I add the __lt__() method: then I have a
slowdown comparable to the one I get using the overridden __eq__, while
the __lt__ method is never called.
Someone can explain me why?
I have here a simple program which shows the behaviour:
*-------------------------------------------------------------------*
#!/usr/bin/env python
import timing
class State(object):
def __init__(self, value):
self.v = value
def generate(self):
return [self.__class__(self.v+1)]
class StateLT(State):
def __lt__ (self, other):
print 'Foo'
return self.v < other.v
class StateEQ(State):
def __eq__ (self, other):
return self.v == other.v
def test(state_cls):
print state_cls
timing.start()
initial = state_cls(0)
l = [initial]
for i in xrange(3000):
successors = l[i].generate()
successors = [s for s in successors if s not in l]
l += successors
timing.finish()
print timing.milli()
if __name__ == '__main__':
test(State)
print ' '
test(StateLT)
print ' '
test(StateEQ)
*-------------------------------------------------------------------*
On my machine the output is:
<class '__main__.State'>
406
<class '__main__.StateLT'>
4982
<class '__main__.StateEQ'>
5395
Here you can see that even with only the __lt__ method it goes 10x
slower, but __lt__ is never called as "Foo" is not printed.
I use the python 2.3.5-8 package on a debian unstable, but even the
python 2.4.3-5 package shows the same behaviour.
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