Steven D'Aprano wrote:
> On Tue, 15 Aug 2006 19:35:11 -0700, KraftDiner wrote:
>
> > I have two classes:
> >
> > class implicitClass:
> > def __init__(self):
> > def isIVR(self): #This is a class private method.
>
> The convention is to flag classes as "private" with a leading underscore:
>
> def _isIVR(self):
>
> or double underscores for "really private, no, honestly":
>
> def __isIVR(self):
>
> but google on "python name mangling" before using that.
>
> [snip]
>
> > As you can see the interface is almost identical.
> >
> > How can I define a base class that will abstract
> > the type such that I don't know if its really and inplicit
> > or explicit object?
>
> Something like this?
>
>
> class baseClass:
> def __init__(self):
> raise NotImplementedError("Don't instantiate the base class!")
> def fromfile(self):
> def getElement(self):
> # etc.
>
>
> class implicitClass(baseClass):
> def __init__(self):
> # code
> def _isIVR(self):
> # code
> def fromfile(self, fileObj, byteOrder):
> # code
> # etc.
>
> Now, you can define instance = implicitClass() or explicitClass(). When
> you come to use instance, you don't need to know whether it is one or the
> other. If you need to type-test, call "isinstance(instance, baseClass)".
>
> The only minor issue is that the fromfile method has a different
> interface. If you really want to do duck typing, they need to have the
> same interface. That might be as simple as:
>
> class explicitClass(baseClass):
> def fromfile(self, fileObj, byteOrder=None):
> # byteOrder is ignored; it is included only for
> # compatibility with implicitClass
>
>
> Is that what you're asking for?
>
Yes I believe so but in fromfile I want to call the appropriate
method depending on the in a parameter in fromfile...
like:
class baseClass:
def fromfile(self, fileObj, byteOrder=None, explicit=False):
if explicit:
call fromfile of explicit class
else:
call fromfile of implicit class
How is that done?
>
>
> --
> Steven D'Aprano
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