For review: PEP 308 - If-then-else expression

[David Gausebeck]

>Adding a keyword doesn't seem to me like a big problem, unless it's a
>keyword that will break a lot of programs (e.g. don't use "n" as a
>keyword).  So here's another alternative:
>
>    ifelse condition: expression1 else: expression2
>
>or if the word "ifelse" is too ugly, we could use a different one instead,
>like maybe "select".
>
>The else clause could be chainable with elif:
>
>    ifelse cond1: exp1 elif cond2: exp2 else: exp3

So this would be exactly like the normal if syntax, except it's an
expression instead of a statement.  This seems like a pretty
good/clean way to handle it.  Also very easy to explain.

It would also be easy to allow defaulting to None. i.e.
ifelse condition: expression1
is equivalent to
ifelse condition: expression1 else: None

I agree that it would benefit from a prettier keyword, though.  I
can't think of anything particularly good... "cond" or "decode" are a
couple more possibilities, though.

-Dave