ENH: fill_value in frame+series flex ops

Author: jbrockmendel

pandas/core/frame.py

@@ -8468,7 +8468,23 @@ def _maybe_align_series_as_frame(self, series: Series, axis: AxisInt):
         blockwise.
         """
         rvalues = series._values
-        if not isinstance(rvalues, np.ndarray):
+        if lib.is_np_dtype(rvalues.dtype):
+            # We can losslessly+cheaply cast to ndarray
+            # i.e. ndarray or dt64[naive], td64
+            # TODO(EA2D): no need to special case with 2D EAs
+            rvalues = np.asarray(rvalues)
+
+            if axis == 0:
+                rvalues = rvalues.reshape(-1, 1)
+            else:
+                rvalues = rvalues.reshape(1, -1)
+
+            rvalues = np.broadcast_to(rvalues, self.shape)
+            # pass dtype to avoid doing inference
+            df = self._constructor(rvalues, dtype=rvalues.dtype)
+
+        else:
+            # GH#61581
             if axis == 0:
                 df = DataFrame(dict.fromkeys(range(self.shape[1]), rvalues))
             else:
@@ -8477,23 +8493,9 @@ def _maybe_align_series_as_frame(self, series: Series, axis: AxisInt):
                     {i: rvalues[[i]].repeat(nrows) for i in range(self.shape[1])},
                     dtype=rvalues.dtype,
                 )
-            df.index = self.index
-            df.columns = self.columns
-            return df
-
-        if axis == 0:
-            rvalues = rvalues.reshape(-1, 1)
-        else:
-            rvalues = rvalues.reshape(1, -1)
-
-        rvalues = np.broadcast_to(rvalues, self.shape)
-        # pass dtype to avoid doing inference
-        return self._constructor(
-            rvalues,
-            index=self.index,
-            columns=self.columns,
-            dtype=rvalues.dtype,
-        ).__finalize__(series)
+        df.index = self.index
+        df.columns = self.columns
+        return df.__finalize__(series)
 
     def _flex_arith_method(
         self, other, op, *, axis: Axis = "columns", level=None, fill_value=None

pandas/tests/arithmetic/test_period.py

@@ -1375,7 +1375,6 @@ def test_period_add_timestamp_raises(self, box_with_array):
 
         with pytest.raises(TypeError, match=msg):
             arr + pd.DataFrame([ts])
-
         with pytest.raises(TypeError, match=msg):
             pd.DataFrame([ts]) + arr
 

pandas/tests/frame/test_arithmetic.py

@@ -659,6 +659,19 @@ def test_arith_flex_series_broadcasting(self, any_real_numpy_dtype):
         result = df.div(df[0], axis="index")
         tm.assert_frame_equal(result, expected)
 
+    def test_arith_flex_zero_len_raises(self):
+        # GH 19522 passing fill_value to frame flex arith methods should
+        # raise even in the zero-length special cases
+        ser_len0 = Series([], dtype=object)
+        df_len0 = DataFrame(columns=["A", "B"])
+        df = DataFrame([[1, 2], [3, 4]], columns=["A", "B"])
+
+        msg = r"unsupported operand type\(s\) for \+: 'int' and 'str'"
+        with pytest.raises(TypeError, match=msg):
+            df.add(ser_len0, fill_value="E")
+
+        df_len0.sub(df["A"], axis=None, fill_value=3)
+
     def test_flex_add_scalar_fill_value(self):
         # GH#12723
         dat = np.array([0, 1, np.nan, 3, 4, 5], dtype="float")