API Provide XSPlotReader.{energies,majorant}; prefer over metadata

serpentTools/parsers/xsplot.py

@@ -34,19 +34,23 @@ class XSPlotReader(BaseReader):
         Contains :class:`~serpentTools.objects.XSData` objects with keys
         given by their names. There should be one XSData instance for each
         isotope and material present in the problem.
+    energies : numpy.ndarray or None
+        Array of energy grids, shared across all XSData instances
+    majorant : numpy.ndarray or None
+        L-inf norm among all macroscopic cross sections used in the problem.
     metadata: dict
-        Contains data pertinent to all XSData instances collected.
-        One particularly important entry is the 'egrid', which is a numpy array
-        of values that define the bin structure XS were recorded in by Serpent.
-        In addition, Serpent defines the 'majorant_xs', which is the L-inf norm
-        among all macroscopic cross sections used in the problem. This gets
-        used in the delta tracking routines usually.
+        Alias for accessing :attr:`energies` and :attr:`majorant`.
+        Attribute-based access is prefered, as this property will
+        likely be removed in the future
+
     """
 
     def __init__(self, filePath):
-        BaseReader.__init__(self, filePath, 'xsplot')
+        super().__init__(filePath, 'xsplot')
         self.xsections = {}
-        self.metadata = {}
+        self.energies = None
+        self.majorant = None
+
     def __len__(self):
         """Number of xsdata objects stored"""
         return len(self.xsections)
@@ -95,6 +99,15 @@ def get(self, key, default=None):
         """
         return self.xsections.get(key, default)
 
+    @property
+    def metadata(self):
+        out = {}
+        if self.energies is not None:
+            out["egrid"] = self.energies
+        if self.majorant is not None:
+            out["majorant_xs"] = self.majorant
+        return out
+
     def _read(self):
         """Read through the depletion file and store requested data."""
         keys = ['E', r'i\d{4,5}', r'm\w']
@@ -107,12 +120,11 @@ def _read(self):
                 data = chunk[1:]
                 if lead.startswith("E = ["):
                     # The energy grid
-                    self.metadata['egrid'] = array(data, dtype=float64)
+                    self.energies = array(data, dtype=float64)
 
                 elif lead.endswith('majorant_xs = ['):
                     # L-inf norm on all XS on all materials
-                    self.metadata['majorant_xs'] = array(data,
-                                                         dtype=float64)
+                    self.majorant = array(data, dtype=float64)
 
                 elif lead.endswith('_mt = ['):
                     xsname = lead[:lead.index("_mt")]