[Python-Dev] Re: PEP 318: Decorators last before colon (original) (raw)

Mark Russell marktrussell at btopenworld.com
Thu Apr 8 19:51:24 EDT 2004

On Mon, 2004-04-05 at 19:03, Guido van Rossum wrote:

> Would it not be possible to cheat and make the lexer transform > > "[" WHITESPACE "as" WHITESPACE IDENTIFIER > > into an LBRACE-AS token (which I assume would make the parser's job > simple).

I don't think without extreme hackery, but feel free to prove me wrong by producing a patch. (A problem is, there could be newlines and comments inside the WHITESPACE. Backtracking over that would require the lexer to have an arbitrary-length buffer.)

Unless I'm missing something (very possible) there's no need to backtrack over the whitespace - all you need is a two-entry stack for the "[" and the token that follows. There's no question of INDENT or DEDENT because we're inside a [] pair. I've put a patch at python.org/sf/932100 which does this, plus changes to Grammar/Grammar, compile.c etc - it implements the syntax:

[as classmethod]
def foo(cls): pass

The newline is optional:

[as foo, bar, baz] def foo(cls): pass

is also legal.

The test suite passes as before (there are still two failures but they are unrelated to this patch). The patch also includes your test_decorators.py, modified for the new syntax.

Mark

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