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

[Andrew Dalke]

Erik Max Francis
> If I see
>
> 's'[:count != 1]
>
> I have to sit and think.

True.  In my code I would have made a temp variable and not worried
about the couple extra lines of code.  Or I would have made that function.

> My example was deliberately simple, to which there are (still in my
> opinion) less clear alternatives.  For _real_ short circuiting, if you
> want that compressed into an expression you have some real IOPyCC
> contenders:

As I pointed out elsewhere, the ternary operator is only rarely used to
prevent side-effects.  In most cases I've seen, there are no differences
with or without short circuiting.

In other words, how often will short circuiting be needed in real code?

David Eppstein pointed out one, with

   if i < 0:
    col = None
  else:
    col = cols[i]

which is nicely expressed as

  col = cols[i] if i < 0 else None

Otherwise, I feel that most real-life problems are more naturally in other
Python idioms.

                    Andrew
                    dalke at dalkescientific.com