Thnx a lot Michael!
For interested:
import new
class MethodDescriptor(object):
def __init__(self, func):
self.func = func
def __get__(self, instance, owner):
if instance is None:
return new.instancemethod(self.func, owner,
owner.__class__)
else:
return new.instancemethod(self.func, instance, owner)
class PropertyDescriptor(object):
def __init__(self, fget, fset, fdel):
self.fget = fget
self.fset = fset
self.fdel = fdel
def __get__(self, instance, owner):
if instance is None:
return self.fget(owner)
else:
return self.fget(instance)
def __set__(self, instance, value):
self.fset(instance, value)
def __delete__(self, instance):
self.fdel(instance)
def hybrid(func):
return MethodDescriptor(func)
def hybrid_property(fget, fset=None, fdel=None):
return PropertyDescriptor(fget, fset, fdel)
class AreaProxy(object):
def __init__(self,s):
self.s=s
def __getattr__(self,key):
return getattr(self.s,"area_"+key)
class Warehouse(object):
def __init__(self,id,construction_id,area_total,area_storage):
self.id = id
self.construction_id = construction_id
self.area_total = area_total
self.area_storage = area_storage
def __repr__(self):
return "%s" % self.id
area = hybrid_property(lambda s: AreaProxy(s))
this works with:
filter()
and returns the value as well
On 13 Paź, 23:04, Michael Bayer <[EMAIL PROTECTED]> wrote:
> OK, take a look at an example we have in examples/derived_attributes/
> attributes.py. This is doing a "dual use" descriptor which works at
> the class level and instance level. Its more complicated but with
> some tweaking can probably work like the example you're giving.
>
> On Oct 13, 2008, at 4:14 PM, g00fy wrote:
>
>
>
> > I did:
>
> > class AreaProxy(object):
> > def __init__(self,parent):
> > self.parent=parent
> > def __getattr__(self, key):
> > return self.parent.area_total
> > return getattr(self.parent, "area_" + key)
> > [EMAIL PROTECTED]
> > def area(self):
> > return Warehouse.AreaProxy(self)
>
> > but when filtering :
>
> > filter(Warehouse.area.total>=100)
> > i get
> > AttributeError: 'property' object has no attribute 'total'
>
> > On 13 Paź, 22:00, g00fy <[EMAIL PROTECTED]> wrote:
> >> I am talking about both.
>
> >> I said it right,
> >> It wasn't working becouse it returned a string column name, and
> >> should
> >> return a value on instance.
> >> And i want to be able to filter by this property also.
>
> >> On 13 Paź, 21:56, Michael Bayer <[EMAIL PROTECTED]> wrote:
>
> >>> On Oct 13, 2008, at 3:40 PM, g00fy wrote:
>
> >>>> I want to:
> >>>> Warehouse.area.total
> >>>> to return
> >>>> Warehouse.area_total
>
> >>>> and so on :
> >>>> Warehouse.area.storage
> >>>> returns:
> >>>> Warehouse.area_storage
>
> >>> then why did you say:
>
> >>>> And this isn't working becouse:
> >>>> Warehouse.area.total
> >>>> returns
> >>>> .area_total
>
> >>> are you talking about class-level SQL predicates, or instance-level
> >>> attribute values ? composite will give you the latter, the
> >>> recipe I
> >>> gave will give you the former. The recipe can be adjusted to
> >>> produce both but its more complicated.
>
>
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