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

[Evan]

Here's a totally new direction: let's get rid of the chaining and 
precedence issues, and make an n-way conditional, not a ternary.

{if cond1: expr1, default}
{if cond1: expr1, cond2: expr2, default}
etc.

Obviously, comma precedence with the braces works the same way as in a 
literal dict.

Examples based on the thread of discussion:

x = {if a < 0: 'negative', a > 0: 'positive', 'zero'}

if {if callable(obj): obj(), alttest()}:

roots = [{if x > 0, sqrt(x), '?'} for x in l]

Cheers,

Evan @ 4-am