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Comment by ericfrederich | Hacker News Reader

... why is this good:

    def dup(n):
        for i in range(n):
            yield i
            yield i

... but this one better?

    def dup(n):
        for i in range(n):
            yield from [i, i]

... it would seem you're needlessly creating (1): another level of generators, and (2) creating a real list

I think for that example it doesn't matter, it is a poor illustration of yield from.

In general `yield from` makes delegation inside a generator cleaner.

Yeah at the very least this should be a tuple rather than a list:

      yield from (i, i)

It does use fewer lines, but if that's the point then this would work:

      yield i; yield i

Compare these instead:

for i in range(n): yield i

yield from range(n)

Both seem quite readable, really.

Seems similar to the usual "list comprehensions vs. for loop" arguments; to which I always think "use whichever is readable for the given code".

The thing about "list comprehensions vs. loop" is that you can compose comprehensions, but you must edit loops to change them.

I fail to see how anything similar would apply here.

The old way hit the interpreter on every loop iteration.