@x.setter property implementation
floris.bruynooghe at gmail.com
Fri Apr 11 12:19:22 CEST 2008
On Apr 11, 10:16 am, Floris Bruynooghe <floris.bruynoo... at gmail.com>
> On Apr 10, 5:09 pm, Arnaud Delobelle <arno... at googlemail.com> wrote:
> > On Apr 10, 3:37 pm, Floris Bruynooghe <floris.bruynoo... at gmail.com>
> > wrote:
> > > On Apr 7, 2:19 pm, "Andrii V. Mishkovskyi" <misho... at gmail.com> wrote:
> > > > 2008/4/7, Floris Bruynooghe <floris.bruynoo... at gmail.com>:
> > > > > Have been grepping all over the place and failed to find it. I found
> > > > > the test module for them, but that doesn't get me very far...
> > > > I think you should take a look at 'descrobject.c' file in 'Objects' directory.
> > > Thanks, I found it! So after some looking around here was my
> > > implementation:
> > > class myproperty(property):
> > > def setter(self, func):
> > > self.fset = func
> > > But that doesn't work since fset is a read only attribute (and all of
> > > this is implemented in C).
> > > So I've settled with the (nearly) original proposal from Guido on
> > > python-dev:
> > > def propset(prop):
> > > assert isinstance(prop, property)
> > > @functools.wraps
> > > def helper(func):
> > > return property(prop.fget, func, prop.fdel, prop.__doc__)
> > > return helper
> > > The downside of this is that upgrade from 2.5 to 2.6 will require code
> > > changes, I was trying to minimise those to just removing an import
> > > statement.
> > > Regards
> > > Floris
> > Here's an implementation of prop.setter in pure python < 2.6, but
> > using sys._getframe, and the only test performed is the one below :)
> > import sys
> > def find_key(mapping, searchval):
> > for key, val in mapping.iteritems():
> > if val == searchval:
> > return key
> > _property = property
> > class property(property):
> > def setter(self, fset):
> > cls_ns = sys._getframe(1).f_locals
> > propname = find_key(cls_ns, self)
> > # if not propname: there's a problem!
> > cls_ns[propname] = property(self.fget, fset,
> > self.fdel, self.__doc__)
> > return fset
> > # getter and deleter can be defined the same way!
> > # -------- Example -------
> > class Foo(object):
> > @property
> > def bar(self):
> > return self._bar
> > @bar.setter
> > def setbar(self, x):
> > self._bar = '<%s>' % x
> > # -------- Interactive test -----
> > >>> foo = Foo()
> > >>> foo.bar = 3
> > >>> foo.bar
> > '<3>'
> > >>> foo.bar = 'oeufs'
> > >>> foo.bar
> > '<oeufs>'
> > Having fun'ly yours,
> Unfortunatly both this one and the one I posted before work when I try
> them out on the commandline but both fail when I try to use them in a
> module. And I just can't figure out why.
This in more detail: Imaging mod.py:
_property = property
"""Python 2.6/3.0 style property"""
def setter(self, fset):
cls_ns = sys._getframe(1).f_locals
for k, v in cls_ns.iteritems():
if v == self:
propname = k
cls_ns[propname] = property(self.fget, fset,
def x(self, v):
self._x = v + 1
Now enter the interpreter:
>>> import mod
>>> f = mod.Foo()
>>> f.x = 4
I don't feel like giving up on this now, so close...
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