[Python-ideas] wild idea : target decorators
Guido van Rossum
guido at python.org
Fri Sep 25 03:19:28 CEST 2009
On Thu, Sep 24, 2009 at 5:38 PM, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:
> I was thinking about something like this myself recently.
> I have some custom property classes that I use extensively
> in a couple of projects, declared like this:
> foo = fancy_property('foo', 'The fancy foo property')
> It would be nice to be able to write this as something
> foo = 'The fancy foo property'
How did one occurrence of 'foo' suddenly turn into foo (without
quotes)? That's not how decorators behave elsewhere.
> or perhaps
> @fancy_property('The fancy foo property')
> foo = default_foo_value
I think the interpretation for decorators on things other than classes
and functions should be derived by carefully reinterpreting what a
decorator does for a function or class.
We already have the rule that
def foo......... # or class foo..........
is equivalent to
def foo.......... # or class foo..........
foo = fancy(foo)
Now in addition we know that
def foo........ # or class foo...........
foo = <create something>
so we have
def foo........ # or class foo.........
as a shorthand for
foo = fancy(<create something>)
>From this we can conclude that
foo = <expression>
foo = fancy(<expression>)
which is (IMO) an utterly unattractive violation of TOOWTDI.
If you were going to object "but def foo and class foo also pass the
string 'foo' into <create something>", my counter-objection is that
those semantics are implied by the def/class keywords and not by the
--Guido van Rossum (home page: http://www.python.org/~guido/)
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