ENH: fill_value in frame+series flex ops

Author: jbrockmendel

pandas/core/frame.py

@@ -8468,27 +8468,34 @@ def _maybe_align_series_as_frame(self, series: Series, axis: AxisInt):
         blockwise.
         """
         rvalues = series._values
-        if not isinstance(rvalues, np.ndarray):
-            # TODO(EA2D): no need to special-case with 2D EAs
-            if rvalues.dtype in ("datetime64[ns]", "timedelta64[ns]"):
-                # We can losslessly+cheaply cast to ndarray
-                rvalues = np.asarray(rvalues)
+        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:
-                return series
+                rvalues = rvalues.reshape(1, -1)
 
-        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)
 
-        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)
+        else:
+            # GH#61581
+            if axis == 0:
+                df = DataFrame(dict.fromkeys(range(self.shape[1]), rvalues))
+            else:
+                nrows = self.shape[0]
+                df = DataFrame(
+                    {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.__finalize__(series)
 
     def _flex_arith_method(
         self, other, op, *, axis: Axis = "columns", level=None, fill_value=None
@@ -8498,11 +8505,6 @@ def _flex_arith_method(
         if self._should_reindex_frame_op(other, op, axis, fill_value, level):
             return self._arith_method_with_reindex(other, op)
 
-        if isinstance(other, Series) and fill_value is not None:
-            # TODO: We could allow this in cases where we end up going
-            #  through the DataFrame path
-            raise NotImplementedError(f"fill_value {fill_value} not supported.")
-
         other = ops.maybe_prepare_scalar_for_op(other, self.shape)
         self, other = self._align_for_op(other, axis, flex=True, level=level)
 

pandas/tests/arithmetic/test_period.py

@@ -1361,12 +1361,8 @@ def test_period_add_timestamp_raises(self, box_with_array):
             arr + ts
         with pytest.raises(TypeError, match=msg):
             ts + arr
-        if box_with_array is pd.DataFrame:
-            # TODO: before implementing resolution-inference we got the same
-            #  message with DataFrame and non-DataFrame.  Why did that change?
-            msg = "cannot add PeriodArray and Timestamp"
-        else:
-            msg = "cannot add PeriodArray and DatetimeArray"
+        
+        msg = "cannot add PeriodArray and DatetimeArray"
         with pytest.raises(TypeError, match=msg):
             arr + Series([ts])
         with pytest.raises(TypeError, match=msg):
@@ -1376,16 +1372,9 @@ def test_period_add_timestamp_raises(self, box_with_array):
         with pytest.raises(TypeError, match=msg):
             pd.Index([ts]) + arr
 
-        if box_with_array is pd.DataFrame:
-            msg = "cannot add PeriodArray and DatetimeArray"
-        else:
-            msg = r"unsupported operand type\(s\) for \+: 'Period' and 'DatetimeArray"
+        msg = "cannot add PeriodArray and DatetimeArray"
         with pytest.raises(TypeError, match=msg):
             arr + pd.DataFrame([ts])
-        if box_with_array is pd.DataFrame:
-            msg = "cannot add PeriodArray and DatetimeArray"
-        else:
-            msg = r"unsupported operand type\(s\) for \+: 'DatetimeArray' and 'Period'"
         with pytest.raises(TypeError, match=msg):
             pd.DataFrame([ts]) + arr
 

pandas/tests/arrays/string_/test_string.py

@@ -249,7 +249,6 @@ def test_mul(dtype):
     tm.assert_extension_array_equal(result, expected)
 
 
-@pytest.mark.xfail(reason="GH-28527")
 def test_add_strings(dtype):
     arr = pd.array(["a", "b", "c", "d"], dtype=dtype)
     df = pd.DataFrame([["t", "y", "v", "w"]], dtype=object)

pandas/tests/frame/test_arithmetic.py

@@ -626,11 +626,9 @@ def test_arith_flex_frame_corner(self, float_frame):
         expected = float_frame.sort_index() * np.nan
         tm.assert_frame_equal(result, expected)
 
-        with pytest.raises(NotImplementedError, match="fill_value"):
-            float_frame.add(float_frame.iloc[0], fill_value=3)
+        res = float_frame.add(float_frame.iloc[0], fill_value=3)
 
-        with pytest.raises(NotImplementedError, match="fill_value"):
-            float_frame.add(float_frame.iloc[0], axis="index", fill_value=3)
+        res = float_frame.add(float_frame.iloc[0], axis="index", fill_value=3)
 
     @pytest.mark.parametrize("op", ["add", "sub", "mul", "mod"])
     def test_arith_flex_series_ops(self, simple_frame, op):
@@ -672,11 +670,11 @@ def test_arith_flex_zero_len_raises(self):
         df_len0 = DataFrame(columns=["A", "B"])
         df = DataFrame([[1, 2], [3, 4]], columns=["A", "B"])
 
-        with pytest.raises(NotImplementedError, match="fill_value"):
+        msg = r"unsupported operand type\(s\) for \+: 'int' and 'str'"
+        with pytest.raises(TypeError, match=msg):
             df.add(ser_len0, fill_value="E")
 
-        with pytest.raises(NotImplementedError, match="fill_value"):
-            df_len0.sub(df["A"], axis=None, fill_value=3)
+        df_len0.sub(df["A"], axis=None, fill_value=3)
 
     def test_flex_add_scalar_fill_value(self):
         # GH#12723