On Wednesday 11 January 2017 12:26, Gerald Britton wrote: > I was rereading the 2.7 docs about abstract base classes the other day. I > found this line in the usage section of the abc.abstractproperty function: > > "This defines a read-only property; you can also define a read-write > abstract property using the ‘long’ form of property declaration:" > > along with an example. so I copied the example and put in a little > surrounding code: > > > from abc import ABCMeta, abstractproperty > > class C(object): > __metaclass__ = ABCMeta > def getx(self): pass > def setx(self, value): pass > x = abstractproperty(getx, setx) > > class D(C): > @property > def x(self):self._x > > d = D() > print(d) > > When I ran this, I expected an exception, since I defined a read/write > abstract property but only implemented the read operation.
I expected the same thing. [...] > If this actually doesn't work (catching the non-implementation at > instantiation time), then would it be appropriate to amend the > documentation? To me at least the doc implies that it *will* raise on the > missing write property implementation (otherwise, what's the point of the > example?) Personally, I consider this a design bug: as designed, abstractproperty is broken. But I couldn't call it a functional bug: it looks like it is working as documented, as useless as that it. Note that in Python 3.3 and better, abstractproperty is deprecated: the ABC metaclass is smart enough to work with the regular property decorator: https://docs.python.org/3.6/library/abc.html#abc.abstractproperty > Or, am I just not grokking it properly? No, I agree with you. I think that a bug request to improve the documentation is appropriate. -- Steven "Ever since I learned about confirmation bias, I've been seeing it everywhere." - Jon Ronson -- https://mail.python.org/mailman/listinfo/python-list
