On 6/9/06, Tim Hochberg <[EMAIL PROTECTED]> wrote: > Sasha wrote: > ... > >> > >My rule of thumb for choosing between an attribute and a method is > >that attribute access should not create new objects. > > > Conceptually at least, couldn't there be a single __array_interface__ > object associated with a given array? In that sense, it doesn't really > feel like creating a new object. > In my view, conceptually, __array_interface__ creates a adaptor to the array-like object. What are the advantages of it being an attribute? It is never settable, so the most common advantage of packing get/set methods in a single attribute can be rulled out. Saving typing of '()' cannot be taken seriousely when the name contains a pair of double underscores :-).
There was a similar issue discussed on the python-3000 mailing list with respect to __hash__ method <http://mail.python.org/pipermail/python-3000/2006-April/000362.html>. > .... > >> > >My problem with __array_struct__ returning either a tuple or a CObject > >is that array protocol sholuld really provide both. CObject is > >useless for interoperability at python level and a tuple (or dict) is > >inefficient at the C level. Thus a good array-like object should > >really provide both __array_struct__ for use by C modules and > >__array_tuple__ (or whatever) for use by python modules. On the other > >hand, making both required attributes/methods will put an extra burden > >on package writers. Moreover, a pure python implementation of an > >array-like object will not be able to provide __array_struct__ at all. > > One possible solution would be an array protocol metaclass that adds > >__array_struct__ to a class with __array_tuple__ and __array_tuple__ > >to a class with __array_struct__ (yet another argument to make both > >methods). > > > > > I don't understand this. I'm don't see how bringing in metaclass is > going to help a pure python type provide a sensible __array_struct__. > That seems like a hopeless task. Shouldn't pure python implementations > just provide __array__? > My metaclass idea is very similar to your unpack_interface suggestion. A metaclass can autonatically add def __array_tuple__(self): return unpack_interface(self.__array_interface__()) or def __array_interface__(self): return pack_interface(self.__array_tuple__()) to a class that only implements only one of the two required methods. > A single attribute seems pretty appealing to me, I'm don't see much use > for anything else. I don't mind just having __array_struct__ that must return a CObject. My main objection was against a method/attribute that may return either CObject or something else. That felt like shifting the burden from package writer to the package user. _______________________________________________ Numpy-discussion mailing list Numpy-discussion@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/numpy-discussion
