PEP 308: Alternative conditional operator forms

[Tim Peters]

[Erik Max Francis]
> The immediate reaction to this is that it doesn't seem fair in cases
> like:
>
> 	f((x if C else y))
>
> (without the doubled parentheses, it would be illegal).  If you want to
> special-case that one, then the grammar gets more complicated and
> eventually you start wondering why the parentheses should be required
> anyway.
>
> Use parentheses for clarity, sure.  _Require_ them, I don't see.

It seems little-known that Guido implemented conditional expressions for
Python about two years ago:

    http://www.python.org/sf/471421

One of his patch comments there:

    It's hairier than expected because I'm trying to require you to
    put parentheses around it in some cases but not in others.

See the patch for more.