[Python-Dev] Making None a keyword (original) (raw)

Steve Holden sholden@holdenweb.com
Fri, 26 Apr 2002 14:13:14 -0400

----- Original Message ----- From: "Guido van Rossum" <guido@python.org> To: "Tim Peters" <tim.one@comcast.net> Cc: <python-dev@python.org> Sent: Friday, April 26, 2002 11:44 AM Subject: Re: [Python-Dev] Making None a keyword

> [Guido] > > ... > > It needs to add 'None' as an alternative to all other places where > > currently NAME occurs. > > Fudge. None makes no sense anywhere in, e.g., > > dottedname: NAME ('.' NAME)* > > or > > globalstmt: 'global' NAME (',' NAME)* > > but I suppose it has to be allowed for in 2.3 anyway else an existing

Yes, that's (alas) the point. > import None.None.None as None > > would yield a SyntaxError instead of a warning. More realistically, def foo(a, None=None): if a is None: ... I found 4 examples of this in Zope3 alone, and MAL has some too. > Note too that we can't change the generated code at all for 2.3 > unless under the control of a new future statement, else existing > None-abusing code could break. A future statement makes no sense for this, so I guess all we can do in 2.3 is warn about use of None in all contexts except in expressions. This is really too bad -- I wish we could decide to just break code (since it's a clean break) but apparently that's unacceptable to the users.

Wouldn't it be nice if there were a collection of programs (perhaps those owned by registered paranoids, but whatever) that you could use to get statistics about breakage under some syntax change?

Clearly extending this through to run-time would add a huge testing infrastructure that would need maintaining, but allowing people to add their own codes to the syntax-checker base might mollify them a bit about the prospect of future language change.

Call it the PythOnGuard (TM) database. :-) - if your programs would break you'll be mailed before it's committed to production.

Back to the yardwork ...

regards Steve

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