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io.BufferReader.read() returns None #80050

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cmaloney changed the title ~~gh-80050: Update BufferedReader.read around non-blocking~~ gh-80050: Update BufferedReader.read docs around non-blocking

gh-129011: Update comments in FileIO to match current code #129012

cmaloney added 5 commits

February 27, 2025 12:30


          Tweaks around raw.readall

b87870b


          tweak readall, hopefully passes

2119f78


          tweaks

ec7f023


          clss -> class

11b754d


          grammatical tweaking

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Mar 1, 2025

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Mar 7, 2025

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cmaloney added 5 commits

March 11, 2025 16:37


          Update to include behavior around None

59bd2a1

BufferedReader at least just forwards `None` from the underlying stream.

1. `BufferedReader.read(size=10)` `raw.read(size=10)` returns None
2. `BufferedReader.read()` without size, raw implements `readall()` which returns None
3. `BufferedReader.read()` without size, raw doesn't have readall so uses a loop that calls `raw.read()` which returns None.


          tweak

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          Tweak read and read1 None and BlockingIOError comments

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          in read1 refer to EINTR retrying

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          fix doc lint around raw.readinto

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cmaloney commented

May 9, 2025

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          personal review fixes

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cmaloney commented May 19, 2025

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cc: @gpshead

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cmaloney added 2 commits

May 19, 2025 17:57


          Update BufferedIOBase class doc for non-blocking

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          Include characters_written in BlockingReader

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cpython/Lib/test/test_io.py

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Doc/library/io.rst

		number of bytes written. When in non-blocking mode, a
		:exc:`BlockingIOError` is raised if the buffer needs to be written out but
		the raw stream blocks.
		:exc:`BlockingIOError` with :attr:`BlockingIOError.characters_written` set

cmaloney May 19, 2025 •

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characters_written is fairly well tested in this case

Lines 1918 to 1943 in a7f317d

	def test_write_non_blocking(self):
	raw = self.MockNonBlockWriterIO()
	bufio = self.tp(raw, 8)

	self.assertEqual(bufio.write(b"abcd"), 4)
	self.assertEqual(bufio.write(b"efghi"), 5)
	# 1 byte will be written, the rest will be buffered
	raw.block_on(b"k")
	self.assertEqual(bufio.write(b"jklmn"), 5)

	# 8 bytes will be written, 8 will be buffered and the rest will be lost
	raw.block_on(b"0")
	try:
	bufio.write(b"opqrwxyz0123456789")
	except self.BlockingIOError as e:
	written = e.characters_written
	else:
	self.fail("BlockingIOError should have been raised")
	self.assertEqual(written, 16)
	self.assertEqual(raw.pop_written(),
	b"abcdefghijklmnopqrwxyz")

	self.assertEqual(bufio.write(b"ABCDEFGHI"), 9)
	s = raw.pop_written()
	# Previously buffered bytes were flushed
	self.assertTrue(s.startswith(b"01234567A"), s)

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gpshead added needs backport to 3.13

only security fixes

needs backport to 3.14 bugs and security fixes labels

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May 21, 2025 16:02

gpshead merged commit e1f8914 into python:main

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miss-islington-app Bot commented May 21, 2025

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Thanks @cmaloney for the PR, and @gpshead for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14.
🐍🍒⛏🤖

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miss-islington pushed a commit to miss-islington/cpython that referenced this pull request


          pythongh-80050: Update BufferedReader.read docs around non-blocking (p…

54a7841

…ythonGH-130653)

(cherry picked from commit e1f8914)

Co-authored-by: Cody Maloney <[email protected]>

miss-islington-app Bot commented May 21, 2025

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Sorry, @cmaloney and @gpshead, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker e1f891414b2329414a6160ed246f5f869a218bfd 3.13

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bedevere-app Bot commented May 21, 2025

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GH-134444 is a backport of this pull request to the 3.14 branch.

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bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label

cmaloney deleted the docs_buffferedreader branch

May 21, 2025 16:07

cmaloney mentioned this pull request

The io module doesn't support non-blocking files #57531

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gpshead pushed a commit that referenced this pull request


          [3.14] gh-80050: Update BufferedReader.read docs around non-blocking (G…

df6d9e7

…H-130653) (#134444)

gh-80050: Update BufferedReader.read docs around non-blocking (GH-130653)
(cherry picked from commit e1f8914)

Co-authored-by: Cody Maloney <[email protected]>

gpshead pushed a commit to gpshead/cpython that referenced this pull request


          [3.13] pythongh-80050: Update BufferedReader.read docs around non-blo…

6f42565

…cking (pythonGH-130653)

(cherry picked from commit e1f8914)

Co-authored-by: Cody Maloney <[email protected]>

bedevere-app Bot commented May 21, 2025

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GH-134445 is a backport of this pull request to the 3.13 branch.

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bedevere-app Bot removed the needs backport to 3.13 only security fixes label

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