On Tue, 15 Nov 2005 18:44:23 +0100, bruno at modulix wrote:
> Another solution to this is the use of a 'marker' object and identity test:
>
> _marker = []
> class A(object):
> def __init__(self, n):
> self.data =n
> def f(self, x = _marker):
> if x is _marker:
> x = self.data
> print x
I would like to see _marker put inside the class' scope. That prevents
somebody from the outside scope easily passing _marker as an argument to
instance.f. It also neatly encapsulates everything A needs within A.
class A(object):
_marker = []
def __init__(self, n):
self.data =n
def f(self, x = _marker):
if x is self.__class__._marker:
# must use "is" and not "=="
x = self.data
print x
Note the gotcha though: in the method definition, you refer to a plain
_marker, but in the method code block, you need to qualify it.
--
Steven.
--
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