Most compact "X if X else Y" idiom

[Steven D'Aprano]

On Sat, 11 Oct 2008 22:01:46 -0700, jbperez808 wrote:

> I find myself having to do the following:
> 
>   x = (some complex expression)
>   y = x if x else "blah"
> 
> and I was wondering if there is any built-in idiom that can remove the
> need to put (some complex expression) in the temporary variable x.

Use short-circuit Booleans:

y = x or "blah"

If x is any true value (non-zero number, non-empty string etc.) then y 
will be set to x; but if x is any false value (zero, empty string, None, 
empty list, etc.) then y will be set to "blah".


However, this technique doesn't work for arbitrary tests. For example, 
you can't simplify the following:

x = (some complex expression)
y = x if 100<=x<250 else "blah"

(at least I can't think of any way).





-- 
Steven