ENH: refactoring sparse classes to create SparseArray subclass for SparseSeries re: #436

Author: wesm

pandas/__init__.py

@@ -28,3 +28,6 @@
 from pandas.util.testing import debug
 
 from pandas.tools.pivot import pivot_table
+
+from pandas.sparse.api import (SparseArray, SparseSeries, SparseDataFrame,
+                               SparsePanel)

pandas/core/api.py

@@ -13,7 +13,6 @@
 from pandas.core.panel import Panel, LongPanel
 from pandas.core.groupby import groupby
 from pandas.core.reshape import pivot_simple as pivot
-from pandas.core.sparse import SparseSeries, SparseDataFrame, SparsePanel
 
 DataMatrix = DataFrame
 WidePanel = Panel

pandas/core/common.py

@@ -660,6 +660,9 @@ def _asarray_tuplesafe(values, dtype=None):
 
     return result
 
+def is_integer(obj):
+    return isinstance(obj, (int, np.integer))
+
 def is_integer_dtype(arr):
     return issubclass(arr.dtype.type, np.integer)
 

pandas/core/series.py

@@ -1433,8 +1433,9 @@ def _align_series(series, indexer):
                     new_values = series.values.copy()
                 else:
                     new_values = series.values
-            result = Series(new_values, join_index, name=series.name)
-            return result
+
+            # be subclass-friendly
+            return series._constructor(new_values, join_index, name=series.name)
 
         left = _align_series(self, lidx)
         right = _align_series(other, ridx)

pandas/sparse/api.py

@@ -0,0 +1,4 @@
+from pandas.sparse.array import SparseArray
+from pandas.sparse.series import SparseSeries
+from pandas.sparse.frame import SparseDataFrame
+from pandas.sparse.panel import SparsePanel