Fixed bug pandas-dev#9733 where stat functions returned a python scalar for empty series

Author: remiremi

pandas/core/nanops.py

@@ -76,7 +76,7 @@ def f(values, axis=None, skipna=True, **kwds):
                         # wrap the 0's if needed
                         if is_timedelta64_dtype(values):
                             return lib.Timedelta(0)
-                        return 0
+                        return values.dtype.type(0)
                     else:
                         result_shape = (values.shape[:axis] +
                                         values.shape[axis + 1:])

pandas/tests/test_series.py

@@ -2592,6 +2592,12 @@ def testit():
                 self.assertRaisesRegexp(NotImplementedError, name, f,
                                         self.series, numeric_only=True)
 
+            # Test type of empty Series
+            s = Series()
+            self.assertEqual(s.dtype, s.sum().dtype)
+            s = Series(dtype=np.int64)
+            self.assertEqual(s.dtype, s.sum().dtype)
+
         testit()
 
         try: