[Python-Dev] Re: Decorators: vertical bar syntax

[Terry Reedy]

"Edward Loper" <edloper at gradient.cis.upenn.edu> wrote in message
news:41145C05.1020501 at gradient.cis.upenn.edu...
> The new "vertical bar" syntax was proposed recently, and has gotten
> almost unanimously positive feedback.  In particular, of 17 responses
> to the syntax, only one has been negative (see table, below).

Add another +1.  Verticle rules have been used before to tie several lines
together, either as continuation lines or as sub-lines.

>      |classmethod
>      |accepts(int, int)
>      |returns(float)
>      def foo(arg1, arg2):
>          ...
>
>      def foo(arg1, arg2):
>          |classmethod
>          |accepts(int, int)
>          |returns(float)
>          ...
> (I prefer the second, but would be happy with either.)

Both logically and visually, I prefer the second also.  By logically, I
mean that it is more meaningful to me to read the decorators after reading
that we are defining a function.

My main objection is that I like the idea that the header is definition
time info and the body is run time code.  I consider the doc string in the
body to be a wart, not a precedence to by copied, but maybe I should think
of the body as starting after the last | or the closing ''' :-).

> The one negative comment was that "|" can look similar to "I" or "l",
> depending on the font; but it's only an issue for some fonts, and it
> should be largely mitigated by syntax-highlighting.

Is a space allowed after the prefic character, whatever it might be?  With

def foo():
   | classmethod
   | accepts(int,int)
   | returns(float)

the visual similarity to I doesn't matter much.  Actual typos leading to
test such as 'I returns' are guaranteed syntax errors, whereas a name such
as Ireturns is not.  The space even more clearly matches standard usage of
a vertical rule and more clearly denotes the list as hanging off of 'def',
so I would be tempted to require the space.

Terry J. Reedy