fixup! ENH: Native conversion from/to scipy.sparse matrix to SparseDataFrame

Author: kernc

Diff for: pandas/sparse/array.py

@@ -20,6 +20,7 @@
                                  is_integer_dtype,
                                  is_bool_dtype,
                                  is_list_like,
+                                 is_string_dtype,
                                  is_scalar, is_dtype_equal)
 from pandas.types.cast import (_possibly_convert_platform, _maybe_promote,
                                _astype_nansafe, _find_common_type)
@@ -769,10 +770,13 @@ def make_sparse(arr, kind='block', fill_value=None):
     if isnull(fill_value):
         mask = notnull(arr)
     else:
-        mask = np.not_equal(arr, fill_value)
-        # In NumPy 1.12.0, not implemented at least for arr.dtype=str
-        if mask is NotImplemented:
-            mask = np.not_equal(arr.astype(object), fill_value)
+        # For str arrays in NumPy 1.12.0, operator!= below isn't
+        # element-wise but just returns False if fill_value is not str,
+        # so cast to object comparison to be safe
+        if is_string_dtype(arr):
+            arr = arr.astype(object)
+
+        mask = arr != fill_value
 
     length = len(arr)
     if length != mask.size: