Init field within Field class

scipp · Nov 20, 2024 · f72aff4 · f72aff4
1 parent 44ebeb6
commit f72aff4
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Showing 4 changed files with 31 additions and 38 deletions.
diff --git a/src/scippnexus/base.py b/src/scippnexus/base.py
@@ -41,45 +41,12 @@ def is_dataset(obj: H5Group | H5Dataset) -> bool:
     return hasattr(obj, 'shape')
 
 
-_scipp_dtype = {
-    np.dtype('int8'): sc.DType.int32,
-    np.dtype('int16'): sc.DType.int32,
-    np.dtype('uint8'): sc.DType.int32,
-    np.dtype('uint16'): sc.DType.int32,
-    np.dtype('uint32'): sc.DType.int32,
-    np.dtype('uint64'): sc.DType.int64,
-    np.dtype('int32'): sc.DType.int32,
-    np.dtype('int64'): sc.DType.int64,
-    np.dtype('float32'): sc.DType.float32,
-    np.dtype('float64'): sc.DType.float64,
-    np.dtype('bool'): sc.DType.bool,
-}
-
-
-def _dtype_fromdataset(dataset: H5Dataset) -> sc.DType:
-    return _scipp_dtype.get(dataset.dtype, sc.DType.string)
-
-
-def _squeezed_field_sizes(dataset: H5Dataset) -> dict[str, int]:
-    if (shape := dataset.shape) == (1,):
-        return {}
-    return {f'dim_{i}': size for i, size in enumerate(shape)}
-
-
 class NXobject:
-    def _init_field(self, field: Field):
-        if field.sizes is None:
-            field.sizes = _squeezed_field_sizes(field.dataset)
-        field.dtype = _dtype_fromdataset(field.dataset)
-
     def __init__(self, attrs: dict[str, Any], children: dict[str, Field | Group]):
         """Subclasses should call this in their __init__ method, or ensure that they
         initialize the fields in `children` with the correct sizes and dtypes."""
         self._attrs = attrs
         self._children = children
-        for field in children.values():
-            if isinstance(field, Field):
-                self._init_field(field)
 
     @property
     def unit(self) -> None | sc.Unit:

diff --git a/src/scippnexus/field.py b/src/scippnexus/field.py
@@ -81,6 +81,31 @@ def _as_datetime(obj: Any):
     return None
 
 
+_scipp_dtype = {
+    np.dtype('int8'): sc.DType.int32,
+    np.dtype('int16'): sc.DType.int32,
+    np.dtype('uint8'): sc.DType.int32,
+    np.dtype('uint16'): sc.DType.int32,
+    np.dtype('uint32'): sc.DType.int32,
+    np.dtype('uint64'): sc.DType.int64,
+    np.dtype('int32'): sc.DType.int32,
+    np.dtype('int64'): sc.DType.int64,
+    np.dtype('float32'): sc.DType.float32,
+    np.dtype('float64'): sc.DType.float64,
+    np.dtype('bool'): sc.DType.bool,
+}
+
+
+def _dtype_fromdataset(dataset: H5Dataset) -> sc.DType:
+    return _scipp_dtype.get(dataset.dtype, sc.DType.string)
+
+
+def _squeezed_field_sizes(dataset: H5Dataset) -> dict[str, int]:
+    if (shape := dataset.shape) == (1,):
+        return {}
+    return {f'dim_{i}': size for i, size in enumerate(shape)}
+
+
 @dataclass
 class Field:
     """NeXus field.
@@ -93,6 +118,12 @@ class Field:
     dtype: sc.DType | None = None
     errors: H5Dataset | None = None
 
+    def __post_init__(self) -> None:
+        if self.sizes is None:
+            self.sizes = _squeezed_field_sizes(self.dataset)
+        if self.dtype is None:
+            self.dtype = _dtype_fromdataset(self.dataset)
+
     @cached_property
     def attrs(self) -> dict[str, Any]:
         """The attributes of the dataset.

diff --git a/src/scippnexus/nxdata.py b/src/scippnexus/nxdata.py
@@ -481,7 +481,6 @@ def __init__(self, attrs: dict[str, Any], children: dict[str, Field | Group]):
             for k in list(children):
                 if k.startswith(name):
                     field = children.pop(k)
-                    self._init_field(field)
                     field.sizes = {
                         'time' if i == 0 else f'dim_{i}': size
                         for i, size in enumerate(field.dataset.shape)

diff --git a/src/scippnexus/nxtransformations.py b/src/scippnexus/nxtransformations.py
@@ -314,13 +314,9 @@ def _locate_depends_on_target(
     target = file[target_path.as_posix()]
 
     if is_dataset(target):
-        from .base import _dtype_fromdataset, _squeezed_field_sizes
-
         res = Field(
             target,
             parent=Group(target.parent, definitions=definitions),
-            sizes=_squeezed_field_sizes(target),
-            dtype=_dtype_fromdataset(target),
         )
     else:
         res = Group(target, definitions=definitions)