[Python-ideas] Non-boolean return from __contains__

[Raymond Hettinger]

On Jul 27, 2010, at 11:04 AM, Guido van Rossum wrote:

> On Tue, Jul 27, 2010 at 5:25 PM, Robert Kern <robert.kern at gmail.com> wrote:
>> I've occasionally wished that we could repurpose backticks for expression
>> literals:
>> 
>>  expr = `x + y*z`
>>  assert isinstance(expr, ast.Expression)
> 
> Maybe you could just as well make it a plain string literal and call a
> function that parses it into a parse tree:
> 
> expr = parse("x + y*z")
> assert isinstance(expr, ast.Expression)
> 
> The advantage of this approach is that you can define a different
> language too...

Starting with string literals and a parse function seems like
a great design decision.   It already works and doesn't require
new syntax.  And, as Guido pointed out, it future proofs the
design by freeing the domain specific language from the 
constraints of Python itself.


Raymond