Re: [Python-ideas] PEP 505 -- None-aware operators

On 14 October 2016 at 14:19, אלעזר wrote:

On Fri, Oct 14, 2016 at 4:14 PM Gustavo Carneiro wrote:

...

Sorry if I missed the boat, but only just now saw this PEP.

Glancing through the PEP, I don't see mentioned anywhere the SQL alternative of having a coalesce() function: https://www. postgresql.org/docs/9.6/static/functions-conditional. html#FUNCTIONS-COALESCE-NVL-IFNULL

In Python, something like this:

def coalesce(*args): for arg in args: if arg is not None: return arg return None

Just drop it into builtins, and voila. No need for lengthy discussions about which operator to use because IMHO it needs no operator.

Sure, it's not as sexy as a fancy new operator, nor as headline grabbing, but it is pretty useful.

This has the downside of not being short-circuit - arguments to the function are evaluated eagerly.

I see. short-circuiting is nice to have, sure. But even without it, it's still useful IMHO. If you are worried about not evaluating an argument, then you can just do a normal if statement instead, for the rare cases where this is important: result = arg1 if result is None: result = compute_something() At the very least I would suggest mentioning a simple coalesce() function in the alternatives section of the PEP. coalesce function: Pros: 1. Familiarity, similar to existing function in SQL; 2. No new operator required; Cons: 1. Doesn't short-circuit the expressions; 2. Slightly more verbose than an operator; Thanks. -- Gustavo J. A. M. Carneiro Gambit Research "The universe is always one step beyond logic." -- Frank Herbert