[Python-ideas] if <expression> as <variable>

Chris Angelico rosuav at gmail.com
Thu Sep 7 15:48:29 EDT 2017

On Fri, Sep 8, 2017 at 5:40 AM, Philipp A. <flying-sheep at web.de> wrote:
> sorry, it’s a bit more difficult. this works:
> https://gist.github.com/flying-sheep/86dfcc1bdd71a33fa3483b83e254084c

If this can be made to work - even hackily - can it be added into
contextlib.contextmanager (or technically its helper class)?
Currently, its __enter__ looks like this:

    def __enter__(self):
            return next(self.gen)
        except StopIteration:
            raise RuntimeError("generator didn't yield") from None

If that raise were replaced with the hackiness of skipping the body,
we could wrap everything up nicely:

def iff(thing):
    if thing: yield thing
    # otherwise don't yield

for i in range(1, 11):
    with iff(random.randrange(3)) as val:
        print(i, val) # won't print any zeroes


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