[Python-Dev] conditional expressions? (original) (raw)

Daniel Mahler mahler@cyc.com
Mon, 15 Oct 2001 22:40:47 -0500

Has an if(cond,exp1,exp2) syntax been considered? It would have the advantage that existing syntax sensitive editors would handle without change. I think conditional exprs badly needed, but the if/then/else syntax seems too verbose for use inside expressions.

regards Daniel Mahler

Tim Peters writes:

[Paul Svensson]

... I know there's been a long time request for this feature, supposedly from people coming to Python from C, but what's the real reason for adding it now, without even a PEP ?

The reason for considering it right now is a rapidly closing window of opportunity -- 2.2b1 goes out later this week. A fellow on c.l.py has been plugging away at a PEP, Eric Raymond submitted a working patch for C's ?: in January of 2000, Jim Fulton loved the idea then (but not particularly the ?: spelling), David Ascher reported that lack of a conditional was a FAQ in his classes then, etc etc. Most replies hated the ?: syntax, and Guido eventually remembered (although I think he forgot it this time around) that Algol-60 used the obvious if/then/else. His reply on Mon, 31 Jan 2000 09:36:52 -0500:

The solution can be the same as what Algol used:  'if' outside
parentheses is a statement, and inside parentheses is an expression.
It's a bit of a grammar rearrangement, but totally unambiguous.

However, the added keyword means it won't be in 1.6.  The lively
discussion means that Eric's patch will have a hard time getting
in too...

The only difference between then and now is s/1.6/2.2/.

Does it really add enough to the language to justify the bloat ?

I expect most people would say it does; by definition I'll adjust my beliefs to whatever Guido decides .

Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev