Sliceable MetaData Class

changelog/455.feature.rst

@@ -0,0 +1 @@
+Add Sliceable `~ndcube.meta.Meta` class for axis-associated metadata.

docs/nitpick-exceptions

@@ -16,3 +16,5 @@ py:class a set-like object providing a view on D's keys
 py:class an object providing a view on D's values
 py:class None.  Remove all items from D.
 py:class a shallow copy of D
+py:class v, remove specified key and return the corresponding value.
+py:class None.  Update D from dict/iterable E and F.

ndcube/__init__.py

@@ -9,9 +9,10 @@
 """
 from .extra_coords.extra_coords import ExtraCoords, ExtraCoordsABC
 from .global_coords import GlobalCoords, GlobalCoordsABC
+from .meta import NDMeta
 from .ndcollection import NDCollection
 from .ndcube import NDCube, NDCubeBase
 from .ndcube_sequence import NDCubeSequence, NDCubeSequenceBase
 from .version import version as __version__
 
-__all__ = ['NDCube', 'NDCubeSequence', "NDCollection", "ExtraCoords", "GlobalCoords", "ExtraCoordsABC", "GlobalCoordsABC", "NDCubeBase", "NDCubeSequenceBase", "__version__"]
+__all__ = ['NDCube', 'NDCubeSequence', "Meta", "NDCollection", "ExtraCoords", "GlobalCoords", "ExtraCoordsABC", "GlobalCoordsABC", "NDCubeBase", "NDCubeSequenceBase", "__version__"]

ndcube/conftest.py

@@ -15,7 +15,7 @@
 from astropy.time import Time, TimeDelta
 from astropy.wcs import WCS
 
-from ndcube import ExtraCoords, GlobalCoords, NDCube, NDCubeSequence
+from ndcube import ExtraCoords, GlobalCoords, NDCube, NDCubeSequence, NDMeta
 
 # Force MPL to use non-gui backends for testing.
 try:
@@ -334,6 +334,23 @@ def ndcube_4d_ln_lt_l_t(wcs_4d_t_l_lt_ln):
     return NDCube(data_cube, wcs=wcs_4d_t_l_lt_ln)
 
 
+@pytest.fixture
+def ndcube_4d_axis_aware_meta(wcs_4d_t_l_lt_ln):
+    shape = (5, 8, 10, 12)
+    wcs_4d_t_l_lt_ln.array_shape = shape
+    data_cube = data_nd(shape, dtype=int)
+    meta = NDMeta({"a": "scalar",
+                   "slit position": np.arange(shape[0], dtype=int),
+                   "pixel label": np.arange(np.prod(shape[:2])).reshape(shape[:2]),
+                   "line": ["Si IV"] * shape[2],
+                   "exposure time": ([2] * shape[-1]) * u.s},
+                  axes={"slit position": 0,
+                        "pixel label": (0, 1),
+                        "line": (2,),
+                        "exposure time": 3})
+    return NDCube(data_cube, wcs=wcs_4d_t_l_lt_ln, meta=meta)
+
+
 @pytest.fixture
 def ndcube_4d_uncertainty(wcs_4d_t_l_lt_ln):
     shape = (5, 8, 10, 12)