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Add SimpleSequence as preferred alias for SupportsLenAndGetItem #6099

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Add SimpleSequence as preferred alias for SupportsLenAndGetItem #6099

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Add SimpleSequence as preferred alias for SupportsLenAndGetItem
srittau Sep 30, 2021
fd29b3c
Merge branch 'master' into plain-sequence
srittau Dec 22, 2021
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9 changes: 9 additions & 0 deletions stdlib/_typeshed/__init__.pyi
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,15 @@ class SupportsDivMod(Protocol[_T_contra, _T_co]):
class SupportsRDivMod(Protocol[_T_contra, _T_co]):
def __rdivmod__(self, __other: _T_contra) -> _T_co: ...

# This represents a sequence as defined in the Python documentation:
# https://docs.python.org/3/glossary.html#term-sequence
# collections.abc.Sequence and typing.Sequence are not protocols and
# have additional fields that are often unnecessary.
class SimpleSequence(Protocol[_T_co]):
def __len__(self) -> int: ...
def __getitem__(self, __k: int) -> _T_co: ...

# obsolete, use SimpleSequence instead
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Why not just delete it? It was not marked with # stable.

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I guess if it's used in third party stubs (there seems to be the one single case), under some circumstances you could run into silent loss of type checking. This already ends up happening though, e.g. see #5786 and #5751, so I'd also be inclined to just delete it.

If we don't delete it, we should alias here, though, and still update the annoy stubs

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The annoy stubs were my main concern. If we update them, they won't work, until type checkers have been updated with the latest typeshed. I'd suggest keeping it for a few months.

class SupportsLenAndGetItem(Protocol[_T_co]):
def __len__(self) -> int: ...
def __getitem__(self, __k: int) -> _T_co: ...
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4 changes: 2 additions & 2 deletions stdlib/builtins.pyi
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Expand Up @@ -10,11 +10,11 @@ from _typeshed import (
OpenTextMode,
ReadableBuffer,
Self,
SimpleSequence,
StrOrBytesPath,
SupportsAnext,
SupportsDivMod,
SupportsKeysAndGetItem,
SupportsLenAndGetItem,
SupportsNext,
SupportsRDivMod,
SupportsRichComparison,
Expand Down Expand Up @@ -1367,7 +1367,7 @@ class reversed(Iterator[_T], Generic[_T]):
@overload
def __init__(self, __sequence: Reversible[_T]) -> None: ...
@overload
def __init__(self, __sequence: SupportsLenAndGetItem[_T]) -> None: ...
def __init__(self, __sequence: SimpleSequence[_T]) -> None: ...
def __iter__(self) -> Iterator[_T]: ...
def __next__(self) -> _T: ...

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