Dave Baum <[EMAIL PROTECTED]> wrote: ... > I still think it would be handy to easily specify the expected types of > function arguments. I sometimes write code in this pattern: > > def foo(a, b): > "a, b - instances of Bar" > assert isinstance(a, Bar) > assert isinstance(b, Bar) > # do some stuff
so in 3.0 you'll be able to spell that @checkanddoc def foo(a: Bar, b: Bar): ... for some suitable decorator checkanddoc (and be assured that there will be a bazillion such decorators written to exploit the new syntax, of varying intent and quality). That's why 3.0 introduces that syntax (args can be spelled <name>:<expr>) without giving it any semantics beyond the fact that the info is recorded with the function object and can be introspected from it -- enabling a thousand flowers to bloom in terms of such decorators. > On the downside, this sort of mechanism might do more harm than good. > For one thing, it would really clash with duck typing. For another, > anyone coming to Python from Java/C++ would probably use those > declarations *everywhere*, even when there isn't a good reason to limit > the type. Sure, even more than they currently use wanton isinstance calls (or even worse, type(x)==... checks). But hopefully the new "syntax hook" will also allow GOOD decorators to emerge (e.g., ones doing adaptation rather than mere checks). Alex -- http://mail.python.org/mailman/listinfo/python-list
