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GeezerVison is showing github.com — gh-139871: Fix 3.15 bytearray.take_bytes example by cmaloney · Pull Request #149520 · python/cpython

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@cmaloney

@cmaloney cmaloney commented May 7, 2026 •
edited by bedevere-app Bot
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Currently:

buffer = bytearray(b'abc\ndef')
n = buffer.find(b'\n')
data = bytes(buffer[:n + 1])
del buffer[:n + 1]
assert data == b'abc'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    assert data == b'abc'
           ^^^^^^^^^^^^^^
AssertionError

Adding in the newline both match:

buffer = bytearray(b'abc\ndef')
n = buffer.find(b'\n')
data = bytes(buffer[:n + 1])
del buffer[:n + 1]
assert data == b'abc\n'
assert buffer == bytearray(b'def')

buffer = bytearray(b'abc\ndef')
n = buffer.find(b'\n')
data = buffer.take_bytes(n + 1)
assert data == b'abc\n'
assert buffer == bytearray(b'def')
  • Issue: Add .take_bytes([n]) a zero-copy path from bytearray to bytes #139871

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@cmaloney
pythongh-139871: Fix 3.15 bytearray.take_bytes example
f69ca1c
Currently:
```python
buffer = bytearray(b'abc\ndef')
n = buffer.find(b'\n')
data = bytes(buffer[:n + 1])
del buffer[:n + 1]
assert data == b'abc'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    assert data == b'abc'
           ^^^^^^^^^^^^^^
AssertionError
```

Adding in the `\n` makes the two match:

```python
buffer = bytearray(b'abc\ndef')
n = buffer.find(b'\n')
data = bytes(buffer[:n + 1])
del buffer[:n + 1]
assert data == b'abc\n'
assert buffer == bytearray(b'def')

buffer = bytearray(b'abc\ndef')
n = buffer.find(b'\n')
data = buffer.take_bytes(n + 1)
assert data == b'abc\n'
assert buffer == bytearray(b'def')
```
@cmaloney cmaloney added the 3.15 bugs and security fixes label May 7, 2026
@cmaloney
cmaloney requested a review from AA-Turner as a code owner May 7, 2026 23:53
@bedevere-app bedevere-app Bot added docs Documentation in the Doc dir skip news labels May 7, 2026
@github-project-automation github-project-automation Bot added this to Docs PRs May 7, 2026
@bedevere-app bedevere-app Bot added the awaiting review label May 7, 2026
@github-project-automation github-project-automation Bot moved this to Todo in Docs PRs May 7, 2026
@bedevere-app bedevere-app Bot mentioned this pull request May 7, 2026
Add .take_bytes([n]) a zero-copy path from bytearray to bytes #139871
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@read-the-docs-community

read-the-docs-community Bot commented May 7, 2026

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Documentation build overview

📚 cpython-previews | 🛠️ Build #32595407 | 📁 Comparing f69ca1c against main (49918f5)

  🔍 Preview build  

1 file changed
± whatsnew/3.15.html
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@cmaloney cmaloney added needs backport to 3.15 bugs and security fixes and removed 3.15 bugs and security fixes labels May 9, 2026
JelleZijlstra
JelleZijlstra approved these changes May 9, 2026
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@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting review labels May 9, 2026
@JelleZijlstra
JelleZijlstra merged commit cc5cf14 into python:main May 9, 2026
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@miss-islington-app

miss-islington-app Bot commented May 9, 2026

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Thanks @cmaloney for the PR, and @JelleZijlstra for merging it 🌮🎉.. I'm working now to backport this PR to: 3.15.
🐍🍒⛏🤖

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@bedevere-app bedevere-app Bot removed the awaiting merge label May 9, 2026
@github-project-automation github-project-automation Bot moved this from Todo to Done in Docs PRs May 9, 2026
@bedevere-app

bedevere-app Bot commented May 9, 2026

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GH-149622 is a backport of this pull request to the 3.15 branch.

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@bedevere-app bedevere-app Bot removed the needs backport to 3.15 bugs and security fixes label May 9, 2026
JelleZijlstra pushed a commit that referenced this pull request May 9, 2026
@miss-islington @cmaloney
[3.15] gh-139871: Fix 3.15 bytearray.take_bytes example (GH-149520) (#…
6ba3ea4
…149622)

gh-139871: Fix 3.15 bytearray.take_bytes example (GH-149520)

Currently:
```python
buffer = bytearray(b'abc\ndef')
n = buffer.find(b'\n')
data = bytes(buffer[:n + 1])
del buffer[:n + 1]
assert data == b'abc'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    assert data == b'abc'
           ^^^^^^^^^^^^^^
AssertionError
```

Adding in the `\n` makes the two match:

```python
buffer = bytearray(b'abc\ndef')
n = buffer.find(b'\n')
data = bytes(buffer[:n + 1])
del buffer[:n + 1]
assert data == b'abc\n'
assert buffer == bytearray(b'def')

buffer = bytearray(b'abc\ndef')
n = buffer.find(b'\n')
data = buffer.take_bytes(n + 1)
assert data == b'abc\n'
assert buffer == bytearray(b'def')
```
(cherry picked from commit cc5cf14)

Co-authored-by: Cody Maloney <[email protected]>
@cmaloney
cmaloney deleted the cmaloney/take_bytes_broken_example branch May 9, 2026 22:15
@cmaloney

cmaloney commented May 9, 2026

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Thank you @JelleZijlstra !

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@JelleZijlstra JelleZijlstra JelleZijlstra approved these changes
@AA-Turner AA-Turner Awaiting requested review from AA-Turner AA-Turner is a code owner

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2 participants

@cmaloney @JelleZijlstra
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