[Python-Dev] Re: Call for defense of @decorators

[Guido van Rossum]

> Having just gone through the wiki page again, I think the last example
> under A (quoted below) shows up very plainly the only really serious
> problem with the before-def decorator syntax:
> 
> class TestDecorators(unittest.TestCase):
> 
>     ...
> 
>     def test_dotted(self):
>         decorators = MiscDecorators()
>         @decorators.author('Cleese')
>         def foo(): return 42
>         self.assertEqual(foo(), 42)
>         self.assertEqual(foo.author, 'Cleese')
> 
> Suppose that you were not familiar enough with python to have heard of
> decorators: looking at this code, would you have any idea that the @
> statement (potentially) fundamentally affects the behaviour of the
> foo() function? Is there anything except their proximity to suggest
> that they are interdependent? The only implication that they *might*
> be is the second assertEqual call, and that is by no means obvious.

This an example of bad formatting.  Tests often do that because their
purpose is to test odd corners of functionality, not serve as sample
code.  Given that in typical example code there will always be a blank
line separating the decorator from anything previous (and separating
the body from what follows!) the connection between the decorator and
the def is pretty clear.

Also note that arguments based on partial knowledge of Python can be
used as an argument against pretty much anything (just tweak the
assumptions a bit), and hence have little value.

--Guido van Rossum (home page: http://www.python.org/~guido/)