[Python-Dev] Re: PEP: Defining Unicode Literal Encodings (revision 1.1)

[Guido van Rossum]

> > Explain again why a directive is better than a specially marked
> > comment, when your main goal seems to be to make it easy for
> > non-parsing tools like editors to find it?
> >...
> 
> Parsing tools do need it. The directive changes the file's semantics.
> Both parsing and non-parsing tools need it.

I understand that.

> I could live with a comment but I think that that is actually harder to
> implement so I don't understand the benefit...I'm still trying to
> understand what tools we are protecting. compiler.py can be easily
> fixed. The real parser/compiler can be easily fixed. The other tools
> mostly take their cue from one of these two modules, right?

I disagree with the first sentence -- I believe a comment is easier to
implement.  The directive statement is still problematic.  Martin's
hack falls short of doing the right thing in all cases: you can't have
the first statement of your program be "directive = ..." or
"directive(...)".

Another argument for a comment: I expect there could be situations
where you want to declare an encoding that doesn't affect the Python
parser, but that does affect the editor (e.g. when you use the
encoding only in comments and/or 8-bit strings).  A comment would
back-port to older Python versions; a directive statement wouldn't.  I
don't know how important this is though.

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