[Python-ideas] Statements vs Expressions... why?

[Arnaud Delobelle]

On 10 Sep 2008, at 22:22, Cliff Wells wrote:

> On Wed, 2008-09-10 at 21:46 +0200, Christian Heimes wrote:
>> Cliff Wells wrote:
>>> Any thoughts on this?  I'm sure it's been brought up before, but I
>>> haven't found any definitive discussions on why this rather  
>>> arbitrary
>>> design decision continues to hold in the face of a general migration
>>> away from imperative languages (especially when it seems it could be
>>> changed without much backwards-compatibility issues).
>>
>> Two thoughts:
>>
>> Please elaborate how you like to change the syntax of Python.
>
> No changes.  Simply lifting of a particular restriction.
>
>> I like to
>> see some concrete examples how your syntax would look like. I also  
>> like
>> to know how your are planing to implement features like lazy  
>> evaluation.
>> The if else ternary operator statement is evaluated lazy. The same
>> construct as expression wouldn't be lazy any more.
>
> Why not?
>
> a = (
>    if a > 1 then:
>        long_calculation()
>    else:
>        other_long_calculation()
> )
>
> Clearly only one of these blocks would be evaluated at runtime.

So what does:

a = (if False: 1)

evaluate to?

-- 
Arnaud