On 12 Mar 2005 09:48:42 -0800, "Martin Miller" <[EMAIL PROTECTED]> wrote:
>I'm trying to create some read-only instance specific properties, but >the following attempt didn't work: > >> class Foobar(object): >> pass >> >> foobar = Foobar() >> foobar.x = property(fget=lambda: 42) >> >> print "foobar.x:", foobar.x > >Which results in the following ouput instead of '42': > foobar.x: <property object at 0x00AE57B0> > >I also tried this: >> foobar.__dict__['x'] = property(fget=lambda: 42) >but get the same behavior. > >Can anyone tell me what's wrong with this approach (and perhaps the >correct way to do it, if there is one)? > One way is to doctor the instance attribute access to do what happens with a property when it is implemented normally as an attribute of the class. E.g., (using InstProp in place of your Foobar) >>> class InstProp(object): ... def __getattribute__(self, attr): ... p = object.__getattribute__(self, attr) ... if isinstance(p, property): return p.__get__(self) ... return p ... >>> import time >>> inst1 = InstProp() >>> inst2 = InstProp() >>> inst1.t = property(lambda self: time.ctime()) >>> inst2.p2 = property(lambda self: 'prop2') >>> inst1.t 'Sat Mar 12 19:10:40 2005' >>> inst2.p2 'prop2' If you want robust writeable and/or deleteable properties, you will have to do a little more work, but it can be done. Regards, Bengt Richter -- http://mail.python.org/mailman/listinfo/python-list
