I don't use isinstance() and type() at all, nor am I testing the type of all variables being passed into function. What I'm arguing for here is a semantic safety mechanism that is neither required, nor imposed. Ultimately what it looks like what I'm proposing is a syntactic shorthand for the adapt() proposal. Which, if other developers have called for, makes my need not so far fetched.
-- http://mail.python.org/mailman/listinfo/python-list