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bpo-27646: Say that 'yield from' expression can be any iterable #24595

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merged 1 commit into from
Feb 21, 2021

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@terryjreedy terryjreedy commented Feb 20, 2021

When ``yield from <expr>`` is used, it treats the supplied expression as
a subiterator. All values produced by that subiterator are passed directly
When ``yield from <expr>`` is used, the supplied expression must be an
iterable. The values produced by iterating that iterable are passed directly
to the caller of the current generator's methods. Any values passed in with
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Is "the current generator's methods" the correct term to use here? (Should it be "the current generator method" or something like that?)

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Good question. I believe the answer is yes, this part of the doc was and is correct. The 'current generator' is the one with 'yield from'. The two methods for getting yielded values are __next__ and send.

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methods could be expanded to '__next__' or 'send' method. (with markup). I notice that the two methods to pass things into the generator are explicitly named in the next sentence. What do you think?

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I see what you mean. Though I'm not sure "passed directly to the caller of ... " is that clear either. Maybe this whole sentence can be rephrased/simplified?

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"The values produced by iterating that iterable form part of the current generator's output." or some such?

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I want to stick with the defined scope of the issue, to replace the ambiguous or incorrect 'subiterator' in these two sentences, so it is clear what one can pass to 'yield from'. Do you have any comment on my replacements?. After sleeping on them, I think them good enough and am ready to merge.

I have also wondered about the exact meaning of 'passed directly', but the visible effect would what lines of code appear in a trace. Does 'passed directly' mean that the 'yield from' line would not appear? I suspect so; but if I cared I would run experiments. I consider this a separate issue.

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Yes, the part you changed looks fine.

@terryjreedy terryjreedy merged commit 2f9ef51 into python:master Feb 21, 2021
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Thanks @terryjreedy for the PR 🌮🎉.. I'm working now to backport this PR to: 3.8, 3.9.
🐍🍒⛏🤖

@terryjreedy terryjreedy deleted the yield-it branch February 21, 2021 02:33
miss-islington pushed a commit to miss-islington/cpython that referenced this pull request Feb 21, 2021
…onGH-24595)

Previously, the doc at least strongly implied that it had to be an iterator.
(cherry picked from commit 2f9ef51)

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>
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GH-24602 is a backport of this pull request to the 3.9 branch.

@bedevere-bot bedevere-bot removed the needs backport to 3.9 only security fixes label Feb 21, 2021
miss-islington pushed a commit to miss-islington/cpython that referenced this pull request Feb 21, 2021
…onGH-24595)

Previously, the doc at least strongly implied that it had to be an iterator.
(cherry picked from commit 2f9ef51)

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>
@bedevere-bot
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GH-24603 is a backport of this pull request to the 3.8 branch.

miss-islington added a commit that referenced this pull request Feb 21, 2021
…4595)

Previously, the doc at least strongly implied that it had to be an iterator.
(cherry picked from commit 2f9ef51)

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>
miss-islington added a commit that referenced this pull request Feb 21, 2021
…4595)

Previously, the doc at least strongly implied that it had to be an iterator.
(cherry picked from commit 2f9ef51)

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>
adorilson pushed a commit to adorilson/cpython that referenced this pull request Mar 13, 2021
…onGH-24595)

Previously, the doc at least strongly implied that it had to be an iterator.
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5 participants