[Info] PEP 308 accepted - new conditional expressions

[Reinhold Birkenfeld]

Rocco Moretti wrote:
> Reinhold Birkenfeld wrote:
>> Hi,
>> 
>> after Guido's pronouncement yesterday, in one of the next versions of Python
>> there will be a conditional expression with the following syntax:
>> 
>> X if C else Y
> 
> Any word on chaining?
> 
> That is, what would happen with the following constructs:
> 
> A if B else C if D else F
> A if B if C else D else F
> 
> The first one is the tricky bit - it could be either
> 
> (A if B else C) if D else F
> or
> A if B else (C if D else F)
> 
> I'd expect the former from left-> right semantics, but reading the 
> unparenthesized form, I'd see "A if B else ..." note that B is true, and 
> conclude the expression evaluated to A (which would be wrong if D is false).

It will be

A if B else (C if D else F).

Quote:
"""
The priorities will be such that you can write

    x = A if C else B
    x = lambda: A if C else B
    x = A if C else B if D else E

But you'd have to write

    if (A if C else B):
    [x for x in seq if (A if C else B)]
    A if (X if C else Y) else B
    (A if C else B) if D else E

Note that all these are intentionally ugly.  :)
"""

Reinhold