Only exposed coord properties for coord types present in wcs and/or e…

…xtra_coords.

ndcube/coords.py

@@ -5,8 +5,23 @@ def __init__(self, ndcube):
         if not isinstance(ndcube, NDCubeABC):
             raise TypeError("ndcube must be an instance of NDCubeABC.")
         self._ndcube = ndcube
+        # Create aliases to coordinate methods already on NDCube.
         self.axis_world_coords = self._ndcube.axis_world_coords
         self.axis_world_coords_values = self._ndcube.axis_world_coords_values
+        # Exposure properties to get values of coordinate types based on
+        # physical types present in NDCube.wcs and NDCube.extra_coords.
+        self._celestial_words = ["pos"]
+        self._time_words = ["time"]
+        self._spectral_words = ["em"]
+        self._stokes_words = ["stokes"]
+        if _words_in_physical_types(self._celestial_words)
+            self.celestial = self._celestial
+        if _words_in_physical_types(self._time_words)
+            self.time = self._time
+        if _words_in_physical_types(self._spectral_words)
+            self.spectral = self._spectral
+        if _words_in_physical_types(self._stokes_words)
+            self.stokes = self._stokes
 
     @property
     def wcs(self):
@@ -28,8 +43,8 @@ def global_coords(self):
     def array_axis_physical_types(self):
         return self._ndcube.array_axis_physical_types
 
-        @property
-    def celestial(self):
+    @property
+    def _celestial(self):
         """
         Returns celestial coordinates for all array indices in relevant axes.
         Celestial world axis physical type name must contain 'pos.'.
@@ -42,10 +57,10 @@ def celestial(self):
         -------
         : `astropy.coordinates.SkyCoord`
         """
-        return self._get_coords_by_word("pos")
+        return self._get_coords_by_word(self._celestial_words)
 
     @property
-    def time(self):
+    def _time(self):
         """
         Returns time coordinates for all array indices in relevant axes.
         Time world axis physical type name must contain 'time'.
@@ -58,10 +73,10 @@ def time(self):
         -------
         : `astropy.time.Time`
         """
-        return self._get_coords_by_word("time")
+        return self._get_coords_by_word(self._time_words)
 
     @property
-    def spectral(self):
+    def _spectral(self):
         """
         Returns spectral coordinates from WCS.
         Spectral world axis physical type name must contain 'em.'.
@@ -74,10 +89,10 @@ def spectral(self):
         -------
         : `astropy.coordinates.SpectralCoord` or `astropy.units.Quantity`
         """
-        return self._get_coords_by_word("em")
+        return self._get_coords_by_word(self._spectral_words)
 
     @property
-    def stokes(self):
+    def _stokes(self):
         """
         Returns stokes polarization for all array indices in relevant axes.
         Stokes world axis physical type name must contain 'stokes'.
@@ -90,39 +105,52 @@ def stokes(self):
         -------
         :
         """
-        return self._get_coords_by_word("stokes")
+        return self._get_coords_by_word(self._stokes_words)
 
     def _get_coords_by_word(self, coord_words):
-            """
-            Returns coordinates from a WCS corresponding to a world axis physical type.
-            """
-            if isinstance(coord_words, str):
-                coord_words = [coord_words]
-            # Check if words are in physical types of main WCS and extra coords.
-            wcs_phys_types = []
-            ec_phys_types = []
-            for wcs, physical_types in zip([self.wcs, self.extra_coords.wcs], [wcs_phys_types, ec_phys_types]):
-                if wcs is not None:
-                    for name in wcs.world_axis_physical_types:
-                        words = set(name.replace(":", ".").split("."))
-                        if any(word in words for word in coord_words):
-                            physical_types.append(name)
-            # Determine type of WCS to use based on whether the words were
-            # found in WCS and/or extra coords.
-            if len(wcs_phys_types) > 0:
-               if len(ec_phys_types) > 0:
-                   wcs = self.combined_wcs
-                   physical_types = wcs_phys_types + ec_phys_types
-               else:
-                   wcs = self.wcs
-                   physical_types = wcs_phys_types
-            elif len(ec_phys_types) > 0:
-                wcs = self.extra_coords
-                physical_types = ec_phys_types
-            else:
-                return None
-            # Calculate coordinates.
-            coords = self.axis_world_coords(*physical_types, wcs=wcs)
-            if len(coords) == 1:
-                coords = coords[0]
-            return coords
+        """
+        Returns coordinates from a WCS corresponding to a world axis physical type.
+        """
+        if isinstance(coord_words, str):
+            coord_words = [coord_words]
+        # Check if words are in physical types of main WCS and extra coords.
+        wcs_phys_types, ec_phys_types = _get_physical_types_from_words(coord_words, [self.wcs, self.extra_coords.wcs])
+        # Determine type of WCS to use based on whether the words were
+        # found in WCS and/or extra coords.
+        if len(wcs_phys_types) > 0:
+           if len(ec_phys_types) > 0:
+               wcs = self.combined_wcs
+               physical_types = wcs_phys_types + ec_phys_types
+           else:
+               wcs = self.wcs
+               physical_types = wcs_phys_types
+        elif len(ec_phys_types) > 0:
+            wcs = self.extra_coords
+            physical_types = ec_phys_types
+        else:
+            return None
+        # Calculate coordinates.
+        coords = self.axis_world_coords(*physical_types, wcs=wcs)
+        if len(coords) == 1:
+            coords = coords[0]
+        return coords
+
+
+def _get_physical_types_from_words(coord_words, wcses):
+    found_phys_types = []
+    for i, wcs in enumerate(wcses):
+        found_phys_types.append([])
+        if wcs is not None:
+            for phys_type in wcs.world_axis_physical_types:
+                words = set(phys_type.replace(":", ".").split("."))
+                if any(word in words for word in coord_words):
+                    found_phys_types[i].append(name)
+    return found_phys_types
+
+
+def _words_in_physical_types(coord_words, wcses):
+    found_phys_types = _get_physical_types_from_words(coord_words, wcses)
+    if any(len(fpt) > 0 for fpt in found_phys_types):
+        return True
+    else:
+        return False