check early for non-scalar default_fill_value (#27302)

Author: jbrockmendel

pandas/core/sparse/frame.py

@@ -6,6 +6,7 @@
 
 import numpy as np
 
+from pandas._libs.lib import is_scalar, item_from_zerodim
 from pandas._libs.sparse import BlockIndex, get_blocks
 from pandas.compat.numpy import function as nv
 from pandas.util._decorators import Appender
@@ -74,6 +75,8 @@ def __init__(
         dtype=None,
         copy=False,
     ):
+        if not is_scalar(default_fill_value):
+            raise ValueError("'default_fill_value' must be a scalar")
 
         warnings.warn(depr_msg, FutureWarning, stacklevel=2)
         # pick up the defaults from the Sparse structures
@@ -666,7 +669,7 @@ def _get_op_result_fill_value(self, other, func):
                 fill_value = np.nan
             else:
                 fill_value = func(np.float64(own_default), np.float64(other.fill_value))
-
+                fill_value = item_from_zerodim(fill_value)
         else:
             raise NotImplementedError(type(other))
 

pandas/tests/sparse/frame/test_frame.py

@@ -136,6 +136,12 @@ def test_constructor(self, float_frame, float_frame_int_kind, float_frame_fill0)
 
         repr(float_frame)
 
+    def test_constructor_fill_value_not_scalar_raises(self):
+        d = {"b": [2, 3], "a": [0, 1]}
+        fill_value = np.array(np.nan)
+        with pytest.raises(ValueError, match="must be a scalar"):
+            SparseDataFrame(data=d, default_fill_value=fill_value)
+
     def test_constructor_dict_order(self):
         # GH19018
         # initialization ordering: by insertion order if python>= 3.6, else