On 12 December 2014 at 22:14, Chris Angelico <ros...@gmail.com> wrote: > On Sat, Dec 13, 2014 at 8:03 AM, Mateusz Loskot <mate...@loskot.net> wrote: >> On 12 December 2014 at 12:26, Chris Angelico <ros...@gmail.com> wrote: >>> On Fri, Dec 12, 2014 at 10:21 PM, Mateusz Loskot <mate...@loskot.net> wrote: >>>> I've got several cases which are not obvious to me. >>>> For instance, class Foo has a boolean attribute, read-write, >>>> which I see a couple of realisations for possible: >>>> >>> >>> 0) Attribute only. >>> >>> class Foo: >>> pass >>> >>> Foo().default = True >>> >>> Unless you need something more than this, go with this style. Much simpler. >> >> >> Agreed, in general, but if the question was related to such simple case, >> I wouldn't bother asking it. >> >> I mentioned, setting the new value involves more changes to Foo() >> instance, so i's not possible to capture it with just an assignment. >> Hence, the discussion between property vs method. > > It's still worth mentioning, for completeness.
Of course, very good point. > Plenty of people come from C++ That's me. > or Java and simply don't realize that direct attribute access > makes fine sense. Your statement here talks about a read-write boolean > attribute, so starting off with the simplest way of doing that - an > actual attribute - emphasizes the commonness of this. Yes, I see your point now. > So, your subsequent design decisions are based around the fact that > you cannot simply assign to .default and have it do the right thing. > Are you even able to set default to False? Right. The particular case (with is_default and make_default members) I'm discussing is similar to this: class Window: def close(self): # operate window so it gets closed @property def is_closed(self) # query state of window > For instance, you might > have a system where there must always be one "default", and so you > can't make this one not-default, but you could make a different one > the default, which will un-default-ify this one as a side effect. In > that case, a "make_default()" method makes the most sense. But if you > can independently and cheaply set any instance's default flag, you > could have the actual attribute, and then a set_default() method, > which updates it. Plenty of Python classes recommend not arbitrarily > altering certain attributes. Yes, makes sense. Thanks for brainstorming those ideas deeper. Best regards, -- Mateusz Loskot, http://mateusz.loskot.net -- https://mail.python.org/mailman/listinfo/python-list