[Python-ideas] Non-boolean return from contains (original) (raw)

Mathias Panzenböck grosser.meister.morti at gmx.net
Tue Jul 27 16:29:56 CEST 2010

On 07/26/2010 04:20 AM, Alex Gaynor wrote:

Fundamentally the argument in favor of it is the same as for the other comparison operators: you want to do symbolic manipulation using the "normal" syntax, as a DSL. My example is that of a SQL expression builder: SQLAlchemy uses User.id == 3 to create a clause where the ID is 3, but for "id in [1, 2, 3]" it has: User.id.in([1, 2, 3]), which is rather unseamly IMO (at least as much as having User.id.eq(3) would be).

This is a bad example for your wish because this code:

id in [1, 2, 3]

translates into:

[1, 2, 3].contains(id)

So it doesn't help that 'in' may return something else than a bool because the method is called on the wrong object for your purposes.

-panzi

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