At 07:32 AM 8/3/04 -0700, Guido van Rossum wrote:
In practical terms, all this means is that I'll just use the hacked syntax until I no longer need to support Python 2.3.
I don't understand why you prefer your hack over the established way to do decorators pre-2.4, which is
def foo(): ... foo = staticmethod(foo)
For the same reason that PEP 318 was written in the first place: to improve readability.
This works across releases (including IronPython), doesn't require any magic, is documented, etc.
True; and most of my existing decorator-using code works this way, and I don't plan on rushing out to change any of it any time soon.
Isn't that much better than spending effort on hacks based on sys.settrace (which are surely going to produce bafflement from users who aren't familiar with that implementation hack)?
Well, up until recently, I thought the [] syntax was still a shoo-in and that the settrace hack was just going to be a way to write backwards-compatible code. In the meantime, I've implemented a predicate-dispatch generic function system using the settrace hack for PyProtocols 1.0, and don't want to have to put off using it until 2.4. (FWIW, I still support 2.2.2, so "until 2.4" means maybe 1-2 years for me.) It looks like this: [when("isinstance(x,Foo) and y>23")] def do_something(x,y): # code for when x is a Foo and y>23 [when("isinstance(x,Bar) and y<99")] def do_something(x,y): # code for when x is a Bar and y<99 Rendered without any decorator syntax, it would have to be something like: def do_something_x_Foo_y_gt_23(x,y): # code for when x is a Foo and y>23 do_something.add("isinstance(x,Foo) and y>23", do_something_x_Foo_y_gt_23) def do_something_x_Bar_y_lt_99(x,y): # code for when x is a Bar and y>99 do_something.add("isinstance(x,Bar) and y>23", do_something_x_Bar_y_lt_99) ...which is a significant loss in readability. Now, it's true that this will just become '@when("whatever")' in 2.4, and I'm *fine* with that, just disappointed that the syntax won't be forward compatible. Indeed, what I'd rather focus on is making sure that the *semantics* will be forward compatible. Which I think they will be. What I'll probably do is make 'when()' and other decorators return a callable that deactivates the trace hack as a side effect of performing the decoration. That way, [when()] and @when() can coexist in a code base during the migration period.