Nick wrote:
Jim Gallacher wrote:
I've only started using properites and I hadn't thought of that. If we
were to use such a feature is that the sort detail that would be
included in the user documentation, or would the coder just be
expected to read the source?
You CAN read the source if you need implementation details, especially
if you're going to override the default behavior. However, in most
cases I think you're going to extend behavior, so you will eventually
call the superclass' getter/setter. A real problem with Python is that
there's no standard convention for writing property getters and
setters. I myself use an idiom like this:
def variable():
def fget(self): return None
def fset(self, value): pass
def fdel(self): pass
doc = """The documentation"""
return locals()
variable = property(**variable())
I like this idiom, because it's really easy to spot in the code, and it
keeps everything together for the property. This forces you to
completely override the property in a subclass, but you don't have to
know the implementation details of the superclass to do that.
Cool.
Another way might be (minimally and traditionally):
def variable_getter(self): return None
def variable_setter(self): pass
variable = property(variable_getter, variable_setter)
which then allows you to override variable_getter or variable_setter in
your subclass without overriding the property itself, but now you've got
to read the code. Or else completely override the property, but you've
got a choice.
My understanding (confired via experimentation) is that with the
'traditional' way you can't orerride the getter or setter originally
bound in by property call. The original methods will be used, not the
ones in the subclass.
class Stuff(object):
def getA(self):
return 'stuff'
a = property(getA)
class MoreStuff(object):
def getA(self):
return 'MORE stuff'
>>> thing = MoreStuff()
>>> print thing.a
stuff
But at any rate, these are basic python questions and I don't think
python-dev is the correct forum for this discussion.
Thanks for giving me a couple of ideas to try out Nick.
Regards,
Jim
