gh-108411: Make typing.IO/BinaryIO arguments positional-only#142906
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JelleZijlstra merged 1 commit intopython:mainfrom Apr 20, 2026
Merged
gh-108411: Make typing.IO/BinaryIO arguments positional-only#142906JelleZijlstra merged 1 commit intopython:mainfrom
JelleZijlstra merged 1 commit intopython:mainfrom
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`IO` is purported to be the type of the file objects returned by `open`. However, all methods on those objects take positional-only arguments, while `IO`'s methods are declared with regular arguments. As such, the file objects cannot actually be considered to implement `IO`. The same thing applies to `BinaryIO`. Fix this by adjusting the definition of these ABCs to match the file objects. This is technically a breaking change, but it is unlikely to actually break anything: * These methods should never be called at runtime, since they are abstract. Therefore, this should not cause any runtime errors. * In typeshed these arguments are already positional-only, so this should not cause any errors during typechecking either.
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JelleZijlstra
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Dec 22, 2025
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@JelleZijlstra Is there anything else that needs to be done to get this merged? |
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IOis purported to be the type of the file objects returned byopen. However, all methods on those objects take positional-only arguments, whileIO's methods are declared with regular arguments. As such, the file objects cannot actually be considered to implementIO. The same thing applies toBinaryIO.Fix this by adjusting the definition of these ABCs to match the file objects.
This is technically a breaking change, but it is unlikely to actually break anything:
These methods should never be called at runtime, since they are abstract. Therefore, this should not cause any runtime errors.
In typeshed these arguments are already positional-only, so this should not cause any errors during typechecking either.