Skip to content

Use contravariant type variable rather than object in Container #15320

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
srittau merged 5 commits into from
Jan 24, 2026
Merged

Use contravariant type variable rather than object in Container #15320

Changes from 3 commits
Commits
Show all changes
5 commits
Select commit Hold shift + click to select a range
53675b6
use 'Any' rather than object in Container
randolf-scholz Jan 24, 2026
2602adc
use contravariant typevar
randolf-scholz Jan 24, 2026
09a0f41
add comment for Container[Any] usage in Collection
randolf-scholz Jan 24, 2026
7201649
make _T_contra default to Any
randolf-scholz Jan 24, 2026
45ebd8a
renamed type var and restored crucial comment
randolf-scholz Jan 24, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
9 changes: 5 additions & 4 deletions stdlib/typing.pyi
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -403,6 +403,7 @@ _S = TypeVar("_S")
_KT = TypeVar("_KT") # Key type.
_VT = TypeVar("_VT") # Value type.
_T_co = TypeVar("_T_co", covariant=True) # Any type covariant containers.
_T_contra = TypeVar("_T_contra", contravariant=True) # Any type contravariant containers.
Comment thread
randolf-scholz marked this conversation as resolved.
Outdated
_KT_co = TypeVar("_KT_co", covariant=True) # Key type covariant containers.
_VT_co = TypeVar("_VT_co", covariant=True) # Value type covariant containers.
_TC = TypeVar("_TC", bound=type[object])
Expand Down Expand Up @@ -641,13 +642,13 @@ class AsyncGenerator(AsyncIterator[_YieldT_co], Protocol[_YieldT_co, _SendT_cont
def aclose(self) -> Coroutine[Any, Any, None]: ...

@runtime_checkable
class Container(Protocol[_T_co]):
# This is generic more on vibes than anything else
Comment thread
randolf-scholz marked this conversation as resolved.
class Container(Protocol[_T_contra]):
@abstractmethod
def __contains__(self, x: object, /) -> bool: ...
def __contains__(self, x: _T_contra, /) -> bool: ...

@runtime_checkable
class Collection(Iterable[_T_co], Container[_T_co], Protocol[_T_co]):
class Collection(Iterable[_T_co], Container[Any], Protocol[_T_co]):
# Note: need to use Container[Any] instead of Container[_T_co] to ensure covariance.
# Implement Sized (but don't have it as a base class).
@abstractmethod
def __len__(self) -> int: ...
Expand Down
Loading