>> wrap scalar values into pandas Series

Author: alixdamman

larray/inout/hdf.py

@@ -3,6 +3,7 @@
 import warnings
 
 import numpy as np
+import pandas as pd
 from pandas import HDFStore
 
 from larray.core.array import Array
@@ -111,13 +112,14 @@ def read_hdf(filepath_or_buffer, key, fill_value=nan, na=nan, sort_rows=False, s
                     key = np.char.decode(key, 'utf-8')
                 axis = read_hdf(filepath_or_buffer, attrs['axis_key'])
                 res = LGroup(key=key, name=name, axis=axis)
+            elif _type == 'scalar':
+                res = pd_obj.values
+                # XXX : assert len(res) == 1 ?
+                if len(res) == 1:
+                    res = res[0]
         except KeyError:
-            scalar_key = key
-            attrs = store.root._v_attrs
-            if scalar_key not in attrs._v_attrnamesuser:
-                filepath = filepath_or_buffer if isinstance(filepath_or_buffer, HDFStore) else store.filename
-                raise KeyError('No item with name {} has been found in file {}'.format(key, filepath))
-            res = attrs[scalar_key]
+            filepath = filepath_or_buffer if isinstance(filepath_or_buffer, HDFStore) else store.filename
+            raise KeyError('No item with name {} has been found in file {}'.format(key, filepath))
     return res
 
 
@@ -132,15 +134,11 @@ def _open_for_read(self):
     def _open_for_write(self):
         self.handle = HDFStore(self.fname)
 
-    @property
-    def attrs(self):
-        return self.handle.root._v_attrs
-
     def list_items(self):
         keys = [key.strip('/') for key in self.handle.keys()]
         items = []
         # scalars
-        items += [(key, 'scalar') for key in self.attrs._v_attrnamesuser if key != 'metadata']
+        items += [(key.split('/')[-1], 'scalar') for key in keys if '__scalars__' in key]
         # axes
         items += [(key.split('/')[-1], 'Axis') for key in keys if '__axes__' in key]
         # groups
@@ -157,7 +155,7 @@ def _read_item(self, key, type, *args, **kwargs):
         elif type == 'Group':
             hdf_key = '__groups__/' + key
         elif type == 'scalar':
-            hdf_key = key
+            hdf_key = '__scalars__/' + key
         else:
             raise TypeError()
         return read_hdf(self.handle, hdf_key, *args, **kwargs)
@@ -174,9 +172,10 @@ def _dump_item(self, key, value, *args, **kwargs):
             hdf_axis_key = '__axes__/' + value.axis.name
             value.to_hdf(self.handle, hdf_key, hdf_axis_key, *args, **kwargs)
         elif isinstance(value, _supported_scalar_types):
-            if key in self.attrs._v_attrnamessys + ['metadata']:
-                raise KeyError("Key '{}' cannot be used because it is a protected name".format(key))
-            self.attrs[key] = value
+            hdf_key = '__scalars__/' + key
+            s = pd.Series(value)
+            self.handle.put(hdf_key, s)
+            self.handle.get_storer(hdf_key).attrs.type = 'scalar'
         else:
             raise TypeError()