Le Thu, 22 Jan 2009 23:29:59 -0000,
"Alan Gauld" <alan.ga...@btinternet.com> a écrit :
>
> "Alan Gauld" <alan.ga...@btinternet.com> wrote
>
> >> is there a way to give arguments to a class definition?
>
> I see that Kent interpreted your question differently to me.
> If you do mean that you want to dynamically define class
> attributes rather than instance attributes then __init__()
> won't work. But I'd be interested to understand why and
> how you would want to do that? And in particular how
> you would use them after creating them?
Thank you Alan and sorry for not having been clear enough. The point actually
was class (definition) attributes. I thought at e.g. Guido's views that lists
were for homogeneous sequences as opposed to tuples rather like records. And a
way to ensure sich a homogeneity, in the sense of items beeing of the same type
or super type.
The straightforward path to ensure that, as I see it, is to add proper argument
to a class definition. But I couldn't find a way to do this. In pseudo-code, it
would look like that:
class MonoList(list, item_type):
typ = item_type
def __init__(self,items):
self._check_types(items)
list.__init__(self,items)
def _check_types(self,items):
for item in items:
if not isinstance(item,MonoList.typ):
message = "blah!"
raise TypeError(message)
def __setitem__(self,index,item):
if not isinstance(item,MonoList.typ):
message = "blah!"
raise TypeError(message)
list.__setitem__(self,index,item)
def __add__(self,other):
self._check_types(other)
list.__add__(self,other)
.......
Well, I realize now that it is a bit more complicated. MonoList itself should
be an intermediate base class between list and and subclasses that each allow
only a single item type. Otherwise all monolist-s have the same item type ;-)
Just exploring around...
denis
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