PERF: Block.apply (pandas-dev#43609)

Author: jbrockmendel

pandas/core/internals/blocks.py

@@ -372,8 +372,7 @@ def apply(self, func, **kwargs) -> list[Block]:
         apply the function to my values; return a block if we are not
         one
         """
-        with np.errstate(all="ignore"):
-            result = func(self.values, **kwargs)
+        result = func(self.values, **kwargs)
 
         return self._split_op_result(result)
 
@@ -399,9 +398,9 @@ def reduce(self, func, ignore_failures: bool = False) -> list[Block]:
         return [nb]
 
     @final
-    def _split_op_result(self, result) -> list[Block]:
+    def _split_op_result(self, result: ArrayLike) -> list[Block]:
         # See also: split_and_operate
-        if is_extension_array_dtype(result) and result.ndim > 1:
+        if result.ndim > 1 and isinstance(result.dtype, ExtensionDtype):
             # TODO(EA2D): unnecessary with 2D EAs
             # if we get a 2D ExtensionArray, we need to split it into 1D pieces
             nbs = []
@@ -415,11 +414,9 @@ def _split_op_result(self, result) -> list[Block]:
                 nbs.append(block)
             return nbs
 
-        if not isinstance(result, Block):
-            result = maybe_coerce_values(result)
-            result = self.make_block(result)
+        nb = self.make_block(result)
 
-        return [result]
+        return [nb]
 
     def fillna(
         self, value, limit=None, inplace: bool = False, downcast=None
@@ -474,7 +471,8 @@ def _split(self) -> list[Block]:
         for i, ref_loc in enumerate(self._mgr_locs):
             vals = self.values[slice(i, i + 1)]
 
-            nb = self.make_block(vals, BlockPlacement(ref_loc))
+            bp = BlockPlacement(ref_loc)
+            nb = type(self)(vals, placement=bp, ndim=2)
             new_blocks.append(nb)
         return new_blocks
 
@@ -647,7 +645,7 @@ def copy(self, deep: bool = True):
         values = self.values
         if deep:
             values = values.copy()
-        return self.make_block_same_class(values)
+        return type(self)(values, placement=self._mgr_locs, ndim=self.ndim)
 
     # ---------------------------------------------------------------------
     # Replace
@@ -1962,16 +1960,15 @@ def get_block_type(dtype: DtypeObj):
     return cls
 
 
-def new_block(values, placement, *, ndim: int, klass=None) -> Block:
+def new_block(values, placement, *, ndim: int) -> Block:
     # caller is responsible for ensuring values is NOT a PandasArray
 
     if not isinstance(placement, BlockPlacement):
         placement = BlockPlacement(placement)
 
     check_ndim(values, placement, ndim)
 
-    if klass is None:
-        klass = get_block_type(values.dtype)
+    klass = get_block_type(values.dtype)
 
     values = maybe_coerce_values(values)
     return klass(values, ndim=ndim, placement=placement)

pandas/tests/apply/test_str.py

@@ -72,8 +72,17 @@ def test_apply_np_reducer(float_frame, op, how):
 @pytest.mark.parametrize("how", ["transform", "apply"])
 def test_apply_np_transformer(float_frame, op, how):
     # GH 39116
-    result = getattr(float_frame, how)(op)
-    expected = getattr(np, op)(float_frame)
+
+    # float_frame will _usually_ have negative values, which will
+    #  trigger the warning here, but let's put one in just to be sure
+    float_frame.iloc[0, 0] = -1.0
+    warn = None
+    if op in ["log", "sqrt"]:
+        warn = RuntimeWarning
+
+    with tm.assert_produces_warning(warn):
+        result = getattr(float_frame, how)(op)
+        expected = getattr(np, op)(float_frame)
     tm.assert_frame_equal(result, expected)