Preamble: when posting a brand new question, you'd better not replying to
an existing completely unrelated message. In most viewers, this will cause
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On Fri, 20 Jun 2008 23:19:37 +0200, Hamish McKenzie
<[EMAIL PROTECTED]> wrote:
I have this class:
class Vector(object):
TOL = 1e-5
def __eq__( self, other, tolerance=TOL ):
print tolerance
shortened for clarity obviously. so I want to subclass this class like
so:
class BigVector(Vector)
TOL = 100
for example if I was working with large vectors which I knew would never
be very close hence the large tolerance. this doesn't work however -
the TOL class variable, while overridden in BigVector, is still using
the Vector.TOL variable in the __eq__ method.
which kinda makes sense to a certain degree, but how do I get the
behaviour where doing:
BigVector().__eq__( otherVec )
prints 100 instead of 1e-5?
does this question make sense? not sure how clearly I'm phrasing my
question... any of you guys python experts?
There's just no way. The default values for function/method arguments are
evaluated when the function definition is interpreted. When the __eq__
method is defined, TOL is 1e-5, so that will be the value used in the
method, whatever you may do afterwards.
I *could* do this, but its ugly:
class Vector(object):
TOL = 1e-5
def __eq__( self, other, tolerance=None ):
if tolerance is None: tolerance = self.TOL
print tolerance
Well, ugliness is in the eye of the beholder... ;-) Even if you find it
ugly, that's the Python way to do it.
HTH
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