On Fri, Feb 23, 2018 at 10:45 AM, Guido van Rossum <guido@python.org> wrote:
There are useful things you can only do with comprehensions if the second for-loop can use the variable in the first for-loop. E.g.
[(i, j) for i in range(10) for j in range(i)]
indeed -- and that is fairly common use-case in nested for loops -- so good to preserve this. But I still think the original: [g(y) for x in range(5) for y in [f(x)]] Is always going to be confusing to read. Though I do agree that it's not too bad when you unpack it into for loops: In [89]: for x in range(5): ...: for y in [f(x)]: ...: l.append(g(y)) BTW, would it be even a tiny bit more efficient to use a tuple in the inner loop? [g(y) for x in range(5) for y in (f(x),)] -CHB -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception Chris.Barker@noaa.gov