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add serializable protocol #3799

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add serializable protocol, and define arrayv3metadata methods that im…
d-v-b Mar 20, 2026
f110af5
Merge branch 'main' into feat/serializable-protocol
d-v-b Mar 20, 2026
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27 changes: 27 additions & 0 deletions src/zarr/abc/serializable.py
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Original file line number Diff line number Diff line change
@@ -0,0 +1,27 @@
from typing import Protocol, Self, TypeVar

T_co = TypeVar("T_co", covariant=True)
T_contra = TypeVar("T_contra", contravariant=True)


class JSONSerializable(Protocol[T_co, T_contra]):
@classmethod
def from_json(cls, obj: T_contra) -> Self:
"""
Deserialize from an instance of T_contra.
"""
...

@classmethod
def try_from_json(cls, obj: object) -> Self:
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@maxrjones maxrjones Mar 20, 2026

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Suggested change
def try_from_json(cls, obj: object) -> Self:
def from_object(cls, obj: object) -> Self:

as discussed on zulip, I'm don't find try_from_json to be intuitive

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@d-v-b d-v-b Mar 20, 2026

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I don't think I'm a fan of from_object, because the term "object" is unfortunately overloaded in python. People might think "object" means "a class instance" as opposed to "the base type object". I'd like to get a range of opinions here. cc @zarr-developers/python-core-devs

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@d-v-b d-v-b Mar 20, 2026

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from_json_checked could convey that there's a type checking step...

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@maxrjones maxrjones Mar 20, 2026

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Could we require typed input for now and add the untyped method later if there's demand?

from_json_checked could convey that there's a type checking step...

I think it could also mean that it's from a checked json. what about from_untyped_json or from_untyped?

"""
Deserialize from an unknown object. Details of any
deserialization failure should be conveyed via an exception.
"""
...

def to_json(self) -> T_co:
"""
Serialize to JSON.
"""
...
4 changes: 2 additions & 2 deletions src/zarr/api/asynchronous.py
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,7 @@
from zarr.core.common import (
JSON,
AccessModeLiteral,
DimensionNames,
DimensionNamesLike,
MemoryOrder,
ZarrFormat,
_default_zarr_format,
Expand Down Expand Up @@ -914,7 +914,7 @@ async def create(
| None
) = None,
codecs: Iterable[Codec | dict[str, JSON]] | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
storage_options: dict[str, Any] | None = None,
config: ArrayConfigLike | None = None,
**kwargs: Any,
Expand Down
8 changes: 4 additions & 4 deletions src/zarr/api/synchronous.py
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Expand Up @@ -33,7 +33,7 @@
from zarr.core.common import (
JSON,
AccessModeLiteral,
DimensionNames,
DimensionNamesLike,
MemoryOrder,
ShapeLike,
ZarrFormat,
Expand Down Expand Up @@ -649,7 +649,7 @@ def create(
| None
) = None,
codecs: Iterable[Codec | dict[str, JSON]] | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
storage_options: dict[str, Any] | None = None,
config: ArrayConfigLike | None = None,
**kwargs: Any,
Expand Down Expand Up @@ -832,7 +832,7 @@ def create_array(
zarr_format: ZarrFormat | None = 3,
attributes: dict[str, JSON] | None = None,
chunk_key_encoding: ChunkKeyEncodingLike | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
storage_options: dict[str, Any] | None = None,
overwrite: bool = False,
config: ArrayConfigLike | None = None,
Expand Down Expand Up @@ -1003,7 +1003,7 @@ def from_array(
zarr_format: ZarrFormat | None = None,
attributes: dict[str, JSON] | None = None,
chunk_key_encoding: ChunkKeyEncodingLike | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
storage_options: dict[str, Any] | None = None,
overwrite: bool = False,
config: ArrayConfigLike | None = None,
Expand Down
30 changes: 15 additions & 15 deletions src/zarr/core/array.py
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Original file line number Diff line number Diff line change
Expand Up @@ -53,7 +53,7 @@
ZARR_JSON,
ZARRAY_JSON,
ZATTRS_JSON,
DimensionNames,
DimensionNamesLike,
MemoryOrder,
ShapeLike,
ZarrFormat,
Expand Down Expand Up @@ -389,7 +389,7 @@ async def create(
| None
) = None,
codecs: Iterable[Codec | dict[str, JSON]] | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
# runtime
overwrite: bool = False,
data: npt.ArrayLike | None = None,
Expand Down Expand Up @@ -417,7 +417,7 @@ async def create(
| None
) = None,
codecs: Iterable[Codec | dict[str, JSON]] | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
# runtime
overwrite: bool = False,
data: npt.ArrayLike | None = None,
Expand Down Expand Up @@ -445,7 +445,7 @@ async def create(
| None
) = None,
codecs: Iterable[Codec | dict[str, JSON]] | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
# v2 only
chunks: ShapeLike | None = None,
dimension_separator: Literal[".", "/"] | None = None,
Expand Down Expand Up @@ -479,7 +479,7 @@ async def create(
| None
) = None,
codecs: Iterable[Codec | dict[str, JSON]] | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
# v2 only
chunks: ShapeLike | None = None,
dimension_separator: Literal[".", "/"] | None = None,
Expand Down Expand Up @@ -630,7 +630,7 @@ async def _create(
| None
) = None,
codecs: Iterable[Codec | dict[str, JSON]] | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
# v2 only
chunks: ShapeLike | None = None,
dimension_separator: Literal[".", "/"] | None = None,
Expand Down Expand Up @@ -742,7 +742,7 @@ def _create_metadata_v3(
fill_value: Any | None = DEFAULT_FILL_VALUE,
chunk_key_encoding: ChunkKeyEncodingLike | None = None,
codecs: Iterable[Codec | dict[str, JSON]] | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
attributes: dict[str, JSON] | None = None,
) -> ArrayV3Metadata:
"""
Expand Down Expand Up @@ -803,7 +803,7 @@ async def _create_v3(
| None
) = None,
codecs: Iterable[Codec | dict[str, JSON]] | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
attributes: dict[str, JSON] | None = None,
overwrite: bool = False,
) -> AsyncArrayV3:
Expand Down Expand Up @@ -1998,7 +1998,7 @@ def create(
| None
) = None,
codecs: Iterable[Codec | dict[str, JSON]] | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
# v2 only
chunks: tuple[int, ...] | None = None,
dimension_separator: Literal[".", "/"] | None = None,
Expand Down Expand Up @@ -2142,7 +2142,7 @@ def _create(
| None
) = None,
codecs: Iterable[Codec | dict[str, JSON]] | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
# v2 only
chunks: tuple[int, ...] | None = None,
dimension_separator: Literal[".", "/"] | None = None,
Expand Down Expand Up @@ -4266,7 +4266,7 @@ async def from_array(
zarr_format: ZarrFormat | None = None,
attributes: dict[str, JSON] | None = None,
chunk_key_encoding: ChunkKeyEncodingLike | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
storage_options: dict[str, Any] | None = None,
overwrite: bool = False,
config: ArrayConfigLike | None = None,
Expand Down Expand Up @@ -4535,7 +4535,7 @@ async def init_array(
zarr_format: ZarrFormat | None = 3,
attributes: dict[str, JSON] | None = None,
chunk_key_encoding: ChunkKeyEncodingLike | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
overwrite: bool = False,
config: ArrayConfigLike | None = None,
) -> AnyAsyncArray:
Expand Down Expand Up @@ -4751,7 +4751,7 @@ async def create_array(
zarr_format: ZarrFormat | None = 3,
attributes: dict[str, JSON] | None = None,
chunk_key_encoding: ChunkKeyEncodingLike | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
storage_options: dict[str, Any] | None = None,
overwrite: bool = False,
config: ArrayConfigLike | None = None,
Expand Down Expand Up @@ -4935,7 +4935,7 @@ def _parse_keep_array_attr(
order: MemoryOrder | None,
zarr_format: ZarrFormat | None,
chunk_key_encoding: ChunkKeyEncodingLike | None,
dimension_names: DimensionNames,
dimension_names: DimensionNamesLike,
) -> tuple[
tuple[int, ...] | Literal["auto"],
ShardsLike | None,
Expand All @@ -4946,7 +4946,7 @@ def _parse_keep_array_attr(
MemoryOrder | None,
ZarrFormat,
ChunkKeyEncodingLike | None,
DimensionNames,
DimensionNamesLike,
]:
if isinstance(data, Array):
if chunks == "keep":
Expand Down
6 changes: 4 additions & 2 deletions src/zarr/core/common.py
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Expand Up @@ -15,6 +15,7 @@
Generic,
Literal,
NotRequired,
TypeAlias,
TypedDict,
TypeVar,
cast,
Expand Down Expand Up @@ -43,11 +44,12 @@
ChunkCoords = tuple[int, ...]
ZarrFormat = Literal[2, 3]
NodeType = Literal["array", "group"]
JSON = str | int | float | bool | Mapping[str, "JSON"] | Sequence["JSON"] | None
JSON: TypeAlias = str | int | float | bool | Mapping[str, "JSON"] | Sequence["JSON"] | None
MemoryOrder = Literal["C", "F"]
AccessModeLiteral = Literal["r", "r+", "a", "w", "w-"]
ANY_ACCESS_MODE: Final = "r", "r+", "a", "w", "w-"
DimensionNames = Iterable[str | None] | None
DimensionNamesLike = Iterable[str | None] | None
DimensionNames = DimensionNamesLike # backwards compatibility

TName = TypeVar("TName", bound=str)
TConfig = TypeVar("TConfig", bound=Mapping[str, object])
Expand Down
10 changes: 5 additions & 5 deletions src/zarr/core/group.py
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Expand Up @@ -40,7 +40,7 @@
ZATTRS_JSON,
ZGROUP_JSON,
ZMETADATA_V2_JSON,
DimensionNames,
DimensionNamesLike,
NodeType,
ShapeLike,
ZarrFormat,
Expand Down Expand Up @@ -1032,7 +1032,7 @@ async def create_array(
order: MemoryOrder | None = None,
attributes: dict[str, JSON] | None = None,
chunk_key_encoding: ChunkKeyEncodingLike | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
storage_options: dict[str, Any] | None = None,
overwrite: bool = False,
config: ArrayConfigLike | None = None,
Expand Down Expand Up @@ -2483,7 +2483,7 @@ def create(
order: MemoryOrder | None = None,
attributes: dict[str, JSON] | None = None,
chunk_key_encoding: ChunkKeyEncodingLike | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
storage_options: dict[str, Any] | None = None,
overwrite: bool = False,
config: ArrayConfigLike | None = None,
Expand Down Expand Up @@ -2627,7 +2627,7 @@ def create_array(
order: MemoryOrder | None = None,
attributes: dict[str, JSON] | None = None,
chunk_key_encoding: ChunkKeyEncodingLike | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
storage_options: dict[str, Any] | None = None,
overwrite: bool = False,
config: ArrayConfigLike | None = None,
Expand Down Expand Up @@ -3025,7 +3025,7 @@ def array(
order: MemoryOrder | None = None,
attributes: dict[str, JSON] | None = None,
chunk_key_encoding: ChunkKeyEncodingLike | None = None,
dimension_names: DimensionNames = None,
dimension_names: DimensionNamesLike = None,
storage_options: dict[str, Any] | None = None,
overwrite: bool = False,
config: ArrayConfigLike | None = None,
Expand Down
8 changes: 5 additions & 3 deletions src/zarr/core/metadata/common.py
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Original file line number Diff line number Diff line change
@@ -1,13 +1,15 @@
from __future__ import annotations

from typing import TYPE_CHECKING
from typing import TYPE_CHECKING, Any

if TYPE_CHECKING:
from collections.abc import Mapping

from zarr.core.common import JSON


def parse_attributes(data: dict[str, JSON] | None) -> dict[str, JSON]:
def parse_attributes(data: Mapping[str, Any] | None) -> dict[str, JSON]:
if data is None:
return {}

return data
return dict(data)
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