[Python-ideas] Accessing the result of comprehension's expression from the conditional

[Jim Jewett]

On Fri, Jun 19, 2009 at 3:39 AM, Lie Ryan<lie.1296 at gmail.com> wrote:

> res = [x**x as F for x in nums if F < 100]

This, I have wanted.

That doesn't resolve all the issues others raised, but (at least for
me), you just moved it from "a little worse than the status quo" to
"hmm... that would be nice if it could be done without too many side
effect on the rest of the language."

On the possibility that a more general problem sometimes spurs a more
elegant solution, I'll point out that I have more often wanted access
to the previous or following element, and that my desired filters on
the results are often reliant on the results-so-far.

> Disadvantages:
> - reverses the current semantic of filtering-then-expression.

For What Its Worth, I'm not sure how strong that argument should be.
Is this just a bizarre corner case, or is there lots of code that
relies on it?

That ordering actually surprises me, because I expect python to
evaluate left to right.

On the other hand, now that we have conditional expressions,
consistency with those is probably more important, so maybe the number
of people surprised by the current situation will go down with time.

-jJ