Bug report

Bug description:

Thememoryview builtin is registered as aSequence, but doesn't implement the full API, because it doesn't inherit fromSequence at runtime and doesn't implement the mixin methods.

>>>importcollections.abc>>>issubclass(memoryview,collections.abc.Sequence)True>>>collections.abc.Sequence.index<functionSequence.indexat0x10148d250>>>>memoryview.indexTraceback (mostrecentcalllast):File"<python-input-4>",line1,in<module>memoryview.indexAttributeError: typeobject'memoryview'hasnoattribute'index'

Among the methods listed for Sequence inthe documentation, memoryview is missing__contains__,__reversed__,index, andcount. This is causing problems for typing; in the typeshed stubs we have to either lie one way by claiming that memoryview has methods it doesn't have, or lie another way by claiming it is not a Sequence whenissubclass() says otherwise at runtime (python/typeshed#12800). To fix this, we should either make memoryview not a Sequence, or add the missing methods. The former has compatibility implications, so I propose to add the methods in 3.14.

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-125420: implementSequence.count API onmemoryview objects #125443
• gh-125420: implementSequence.index API onmemoryview objects #125446
• (under consideration)gh-125420: implementSequence.__contains__ API onmemoryview objects #125441
• (under consideration)gh-125420: implementSequence.__reversed__ API onmemoryview objects #125505