else in list comp

[Alex Martelli]

Cliff Wells wrote:
   ...
> myList = [0, None, '1', None, 2, None, '3']
> 
> My real interest was in a possible "else" clause (as per the subject
> line) in a list comp.
> 
> ['' for i in myList if i is None else i]
> 
> It seems a good idea to me, but then, I'm somewhat biased toward my own
> ideas.

Seems too specialized to me.  I'm strongly biased against adding
stuff to Python.  I might solve this specific problem as follows:

[ [i, ''][i is None] for i in myList ]

IF (a BIG if) this is such a problem that it's worth adding stuff
to Python, then clearly the added stuff must be general -- namely,
a ternary (if not an even wider one-of-N) short-circuiting operator.

See the Python Cookbook for a LOT of discussion of ternary ops
(how to synthesize them in Python, and why no way is 100% OK yet,
although by one idiom or another one gets by without too many
problems about 99.44% of the time).

But limiting the application of such an addition to ONE specific
case, list comprehensions, would be horrible design IMHO.


Alex