thebjorn a écrit : > On Nov 12, 1:05 am, "Anand Patil" <[EMAIL PROTECTED]> > wrote: >> Hi all, >> >> I have two questions about a class, which we'll call MyWrapperClass, >> in a package to which I'm contributing. >> >> 1) MyWrapperClass wraps functions. Each instance has an attribute >> called 'value' and a method called 'eval', which calls the wrapped >> function. An instance D that depends on instances A, B and C can be >> created as follows: >> >> @mywrapperclass >> def D(A, B, C): >> return foo(A.value, B.value, C.value) >> >> Now that D exists, the call D.eval() will work without any arguments >> (D remembers that the arguments are A, B and C and passes their values >> to foo). What is the standard terminology for such classes, and does >> anyone know of a package that implements them in a nice way? (It's >> easy enough to roll our own, but reading about other implementations >> might give us good ideas). >> >> 2) D.eval() will frequently be called multiple times in succession >> before A.value, B.value or C.value has had the chance to change. It >> would be _extremely_ helpful to have D detect this situation and skip >> recomputation. I'm looking for the fastest safe way to do this. >> There's no restriction on what kind of object A.value, etc. are, so >> unfortunately they might be mutable. >> >> Our current solution is to have D compare A.value, B.value and C.value >> to an internal cache using the 'is' operator (and put a big warning in >> the docs about not changing 'value' attributes in-place). Not exactly >> safe, but the speed savings over comparison with '==' will be >> significant. Is this OK, bad or an abomination? >> >> Again it would be helpful to know the terminology associated with the >> behavior I'm looking for and any packages that implement it nicely. >> >> Many thanks in advance and apologies for the long post, >> Anand > > Cells (A dataflow extension to CLOS) seems like what you want: > > http://common-lisp.net/project/cells/ > > I think there was talk of a Python version a while back... > > -- bjorn >
pycells : http://pycells.pdxcb.net/ but also trellis : http://peak.telecommunity.com/DevCenter/Trellis -- http://mail.python.org/mailman/listinfo/python-list
