a Python person's experience with Ruby
Arnaud Delobelle
arnodel at googlemail.com
Sun Dec 9 06:11:04 EST 2007
On Dec 9, 12:15 am, Bruno Desthuilliers
<bdesth.quelquech... at free.quelquepart.fr> wrote:
> Richard Jones a écrit :
>
>
>
> > Bruno Desthuilliers wrote:
>
> >>class A(object):
> >> @apply
> >> def a():
> >> def fget(self):
> >> return self._a
> >> def fset(self, val):
> >> self._a = val
> >> return property(**locals())
> >> def __init__(self):
> >> self.a = "foo"
>
> > That property setup seems overly complicated. As far as I can see, it only
> > avoids defining the setter in the class namespace,
>
> Yes. That's mosly the point.
>
> > yet is more complicated
> > and obfuscated to boot ;)
>
> Well, that's your POV, so what can I say ? It's indeed a bit hackish,
> and requires a couple minutes of attention the first time you see it.
> And you just have to learn it once !-)
Perhaps 'return property(fget, fset)' would be easier to make sense of
than **locals()
> Now I'd certainly prefer something like:
>
> class A(object):
> @propget
> def a(self):
> return self._a
> @propset
> def a(self, val):
> self._a = val
>
> But until there's something similar *builtin*, I'll stick to the @apply
> trick.
At first sight, I like the look of this. Obviously I can't provide a
builtin implementation, but there's an easy way to achieve this. It
uses sys._getframe but there is no need to fiddle with metaclasses:
from sys import _getframe
def _makeprop(frame, name, **d):
p = frame.f_locals.get(name, None)
args = {}
if isinstance(p, property):
args = dict(fget=p.fget, fset=p.fset, fdel=p.fdel,
doc=p.__doc__)
args.update(d)
return property(**args)
def propget(f):
return _makeprop(_getframe(1), f.__name__, fget=f)
def propset(f):
return _makeprop(_getframe(1), f.__name__, fset=f)
def propdel(f):
return _makeprop(_getframe(1), f.__name__, fdel=f)
if __name__ == '__main__':
class Foo(object):
a = property(doc="mod10 attribute")
@propget
def a(self):
return self._a
@propset
def a(self, a):
self._a = a % 10
@propdel
def a(self):
del self._a
f = Foo()
f.a = 42
assert f.a == 42 % 10
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