On 8 Jun 2016, at 17:19, Steven D'Aprano <steve@pearwood.info> wrote:
On Tue, Jun 07, 2016 at 11:17:26PM -0400, Eric V. Smith wrote:
I think we might need some helpers, and a slight change to the specifics. I'd have:
@binding_method x = obj
result in: x = binding_method('x', obj)
That's a bit more promising.
Disadvantage: - what was one line is now two; - confusing to pass more than a single argument (plus the implicit name) to the function; - fails the principle "things that look similar should be similar".
Status quo:
Record = namedtuple('Record', fields)
would become:
@namedtuple Record = fields
which doesn't look awful. I'm sad that it needs two lines.
But what if you want to pass more than one argument?
@namedtuple Record = fields, True
That will be equivalent to
namedtuple('Record', (fields, True))
which is not what is wanted. And it gets worse if you use a keyword argument:
Record = fields, verbose=True
TypeError, can't iterate over boolean @namedtuple(verbose=True) Record = fields Although for namedtuple in particular, I'd rather have namedtuple be a class-generator: class Record(namedtuple(fields)): pass Or class Record(metaclass=namedtuple): fields = fields And namedtuple could abuse all the g(l)ory details of metaclasses and/of eval to do its job. And that is the right solution for namedtuple. The cases that interest me more are typevar/symbol/Django modelfields/sqlalchemy declarative fields and all the cases where you're not constructing a class(like) thingy.
I don't really like the way the @ syntax is being used for two completely different things.
@function def spam(): ...
does one thing, but
@function spam = ...
does a completely different and unrelated thing. I'm not saying that @ cannot be used for anything but decorators, but I think it is confusing to use something which looks so close to decorator syntax for something that is nothing like a decorator.
The question for me is: do we want to have something that tells the compiler that "binding_method" or "namedtuple" above are special, or is this just what the compiler does for all uses of what looks like a decorated assignment statement?
I'm surprised you ask that question :-) What does the Zen say about special cases?
I don't think it is desirable to have developers have to go cap in hand to the core devs and say "Please sir, I have a function that needs to know its name, can you please add it to the privileged list of special functions that work with @ please?"
*wink*
It should either work for any name after the @ or not at all. Hard coding support for just namedtuple would be bad.
-- Steve _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/