Description

encukou

opened on Oct 26, 2022

Issue body actions

The docs say:

Some formats require a read-only bytes-like object, and set a pointer instead of a buffer structure. They work by checking that the object’s PyBufferProcs.bf_releasebuffer field is NULL, which disallows mutable objects such as bytearray.

This can easily be understood that bf_releasebuffer is directly linked to (im)mutability.
In reality this check is there to ensure whether the buffer can be safely "borrowed". For simple buffer exporters (like most of the stdlib ones), this correlates with immutability -- but not always, e.g.:

>>> import unicodedata
>>> unicodedata.lookup(b'SNAKE')  # `lookup` happens to use the s# format internally
'🐍'
>>> view = memoryview(b'SNAKE')
>>> view.readonly
True
>>> unicodedata.lookup(view)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: lookup() argument must be read-only bytes-like object, not memoryview

The docs should explain the semantics precisely, without overwhelming the user that just wants to take str/bytes.

Linked PRs

• [3.10] gh-98712: Clarify "readonly bytes-like object" semantics in C arg-parsing docs (GH-98710) #100461
• [3.11] gh-98712: Clarify "readonly bytes-like object" semantics in C arg-parsing docs (GH-98710) #100462

Activity

1. encukou

   added

   docsDocumentation in the Doc dirDocumentation in the Doc dir

   on Oct 26, 2022
2. JelleZijlstra

   added a commit that references this issue on Dec 23, 2022

   gh-98712: Clarify "readonly bytes-like object" semantics in C arg-par…

   49f6ff7
3. miss-islington

   added 4 commits that reference this issue on Dec 23, 2022

   pythongh-98712: Clarify "readonly bytes-like object" semantics in C a…

   ace96d8

   pythongh-98712: Clarify "readonly bytes-like object" semantics in C a…

   63a6bbc

   gh-98712: Clarify "readonly bytes-like object" semantics in C arg-par…

   4b3b642

   gh-98712: Clarify "readonly bytes-like object" semantics in C arg-par…

   bd47219
4. hauntsaninja commented on Dec 24, 2022

   

   hauntsaninja

   on Dec 24, 2022

   Contributor

   More actions

   Thanks, looks like the backports are all merged
5. hauntsaninja

   closed this as completedon Dec 24, 2022
6. iritkatriel

   added a commit that references this issue on Dec 28, 2022

   Merged main into regmachine branch (#50)

   fdc73cb

Issue actions