fix: add get(key, default) method to Group APIs (#2311)

* fix: add get(key, default) method to Group APIs

* add test

Author: jhamman

src/zarr/core/group.py

@@ -4,7 +4,7 @@
 import json
 import logging
 from dataclasses import asdict, dataclass, field, fields, replace
-from typing import TYPE_CHECKING, Literal, cast, overload
+from typing import TYPE_CHECKING, Literal, TypeVar, cast, overload
 
 import numpy as np
 import numpy.typing as npt
@@ -42,6 +42,8 @@
 
 logger = logging.getLogger("zarr.group")
 
+DefaultT = TypeVar("DefaultT")
+
 
 def parse_zarr_format(data: Any) -> ZarrFormat:
     if data in (2, 3):
@@ -290,6 +292,28 @@ async def delitem(self, key: str) -> None:
         else:
             raise ValueError(f"unexpected zarr_format: {self.metadata.zarr_format}")
 
+    async def get(
+        self, key: str, default: DefaultT | None = None
+    ) -> AsyncArray | AsyncGroup | DefaultT | None:
+        """Obtain a group member, returning default if not found.
+
+        Parameters
+        ----------
+        key : string
+            Group member name.
+        default : object
+            Default value to return if key is not found (default: None).
+
+        Returns
+        -------
+        object
+            Group member (AsyncArray or AsyncGroup) or default if not found.
+        """
+        try:
+            return await self.getitem(key)
+        except KeyError:
+            return default
+
     async def _save_metadata(self, ensure_parents: bool = False) -> None:
         to_save = self.metadata.to_buffer_dict(default_buffer_prototype())
         awaitables = [set_or_delete(self.store_path / key, value) for key, value in to_save.items()]
@@ -828,6 +852,26 @@ def __getitem__(self, path: str) -> Array | Group:
         else:
             return Group(obj)
 
+    def get(self, path: str, default: DefaultT | None = None) -> Array | Group | DefaultT | None:
+        """Obtain a group member, returning default if not found.
+
+        Parameters
+        ----------
+        key : string
+            Group member name.
+        default : object
+            Default value to return if key is not found (default: None).
+
+        Returns
+        -------
+        object
+            Group member (Array or Group) or default if not found.
+        """
+        try:
+            return self[path]
+        except KeyError:
+            return default
+
     def __delitem__(self, key: str) -> None:
         self._sync(self._async_group.delitem(key))
 

tests/v3/test_group.py

@@ -292,6 +292,25 @@ def test_group_getitem(store: Store, zarr_format: ZarrFormat) -> None:
         group["nope"]
 
 
+def test_group_get_with_default(store: Store, zarr_format: ZarrFormat) -> None:
+    group = Group.from_store(store, zarr_format=zarr_format)
+
+    # default behavior
+    result = group.get("subgroup")
+    assert result is None
+
+    # custom default
+    result = group.get("subgroup", 8)
+    assert result == 8
+
+    # now with a group
+    subgroup = group.require_group("subgroup")
+    subgroup.attrs["foo"] = "bar"
+
+    result = group.get("subgroup", 8)
+    assert result.attrs["foo"] == "bar"
+
+
 def test_group_delitem(store: Store, zarr_format: ZarrFormat) -> None:
     """
     Test the `Group.__delitem__` method.