PERF: do ndim validation before Block.__init__

pandas/core/internals/api.py

@@ -14,13 +14,13 @@
 from pandas._typing import Dtype
 
 from pandas.core.dtypes.common import is_datetime64tz_dtype
-from pandas.core.dtypes.dtypes import PandasDtype
-from pandas.core.dtypes.generic import ABCPandasArray
 
 from pandas.core.arrays import DatetimeArray
 from pandas.core.internals.blocks import (
     Block,
     DatetimeTZBlock,
+    check_ndim,
+    extract_pandas_array,
     get_block_type,
 )
 
@@ -39,29 +39,28 @@ def make_block(
     - Block.make_block_same_class
     - Block.__init__
     """
-    if isinstance(values, ABCPandasArray):
-        # Ensure that we don't allow PandasArray / PandasDtype in internals.
-        # For now, blocks should be backed by ndarrays when possible.
-        values = values.to_numpy()
-        if ndim and ndim > 1:
-            # TODO(EA2D): special case not needed with 2D EAs
-            values = np.atleast_2d(values)
-
-    if isinstance(dtype, PandasDtype):
-        dtype = dtype.numpy_dtype
+    values, dtype = extract_pandas_array(values, dtype, ndim)
 
     if klass is None:
         dtype = dtype or values.dtype
         klass = get_block_type(values, dtype)
 
     elif klass is DatetimeTZBlock and not is_datetime64tz_dtype(values.dtype):
-        # TODO: This is no longer hit internally; does it need to be retained
-        #  for e.g. pyarrow?
+        # pyarrow calls get here
         values = DatetimeArray._simple_new(values, dtype=dtype)
 
     if not isinstance(placement, BlockPlacement):
         placement = BlockPlacement(placement)
 
+    ndim = _maybe_infer_ndim(values, placement, ndim)
+    check_ndim(values, placement, ndim)
+    return klass(values, ndim=ndim, placement=placement)
+
+
+def _maybe_infer_ndim(values, placement: BlockPlacement, ndim: Optional[int]) -> int:
+    """
+    If `ndim` is not provided, infer it from placment and values.
+    """
     if ndim is None:
         # GH#38134 Block constructor now assumes ndim is not None
         if not isinstance(values.dtype, np.dtype):
@@ -71,5 +70,4 @@ def make_block(
                 ndim = 2
         else:
             ndim = values.ndim
-
-    return klass(values, ndim=ndim, placement=placement)
+    return ndim

pandas/core/internals/blocks.py

@@ -47,7 +47,6 @@
 )
 from pandas.core.dtypes.common import (
     is_categorical_dtype,
-    is_datetime64tz_dtype,
     is_dtype_equal,
     is_extension_array_dtype,
     is_list_like,
@@ -162,21 +161,10 @@ def __init__(self, values, placement, ndim: int):
         ndim : int
             1 for SingleBlockManager/Series, 2 for BlockManager/DataFrame
         """
-        # TODO(EA2D): ndim will be unnecessary with 2D EAs
-        self.ndim = self._check_ndim(values, ndim)
+        self.ndim = ndim
         self.mgr_locs = placement
         self.values = self._maybe_coerce_values(values)
 
-        if self._validate_ndim and self.ndim and len(self.mgr_locs) != len(self.values):
-            raise ValueError(
-                f"Wrong number of items passed {len(self.values)}, "
-                f"placement implies {len(self.mgr_locs)}"
-            )
-
-        elif self.is_extension and self.ndim == 2 and len(self.mgr_locs) != 1:
-            # TODO(EA2D): check unnecessary with 2D EAs
-            raise AssertionError("block.size != values.size")
-
     @classmethod
     def _maybe_coerce_values(cls, values):
         """
@@ -192,43 +180,6 @@ def _maybe_coerce_values(cls, values):
         """
         return values
 
-    def _check_ndim(self, values, ndim: int):
-        """
-        ndim inference and validation.
-
-        Infers ndim from 'values' if not provided to __init__.
-        Validates that values.ndim and ndim are consistent if and only if
-        the class variable '_validate_ndim' is True.
-
-        Parameters
-        ----------
-        values : array-like
-        ndim : int
-
-        Returns
-        -------
-        ndim : int
-
-        Raises
-        ------
-        ValueError : the number of dimensions do not match
-        """
-        assert isinstance(ndim, int)  # GH#38134 enforce this
-
-        if self._validate_ndim:
-            if values.ndim != ndim:
-                raise ValueError(
-                    "Wrong number of dimensions. "
-                    f"values.ndim != ndim [{values.ndim} != {ndim}]"
-                )
-        elif values.ndim > ndim:
-            # ExtensionBlock
-            raise ValueError(
-                "Wrong number of dimensions. "
-                f"values.ndim > ndim [{values.ndim} > {ndim}]"
-            )
-        return ndim
-
     @property
     def _holder(self):
         """
@@ -378,7 +329,7 @@ def getitem_block(self, slicer, new_mgr_locs=None) -> Block:
 
         new_values = self._slice(slicer)
 
-        if self._validate_ndim and new_values.ndim != self.ndim:
+        if new_values.ndim != self.values.ndim:
             raise ValueError("Only same dim slicing is allowed")
 
         return type(self)._simple_new(new_values, new_mgr_locs, self.ndim)
@@ -2262,9 +2213,63 @@ def get_block_type(values, dtype: Optional[Dtype] = None):
     return cls
 
 
-def new_block(
-    values, placement, klass=None, ndim=None, dtype: Optional[Dtype] = None
-) -> Block:
+def new_block(values, placement, *, ndim: int, klass=None) -> Block:
+
+    if not isinstance(placement, BlockPlacement):
+        placement = BlockPlacement(placement)
+
+    values, _ = extract_pandas_array(values, None, ndim)
+    check_ndim(values, placement, ndim)
+
+    if klass is None:
+        klass = get_block_type(values, values.dtype)
+
+    return klass(values, ndim=ndim, placement=placement)
+
+
+def check_ndim(values, placement: BlockPlacement, ndim: int):
+    """
+    ndim inference and validation.
+
+    Validates that values.ndim and ndim are consistent.
+    Validates that len(values) and len(placement) are consistent.
+
+    Parameters
+    ----------
+    values : array-like
+    placement : BlockPlacement
+    ndim : int
+
+    Raises
+    ------
+    ValueError : the number of dimensions do not match
+    """
+
+    if values.ndim > ndim:
+        # Check for both np.ndarray and ExtensionArray
+        raise ValueError(
+            "Wrong number of dimensions. "
+            f"values.ndim > ndim [{values.ndim} > {ndim}]"
+        )
+
+    elif isinstance(values.dtype, np.dtype):
+        # TODO(EA2D): special case not needed with 2D EAs
+        if values.ndim != ndim:
+            raise ValueError(
+                "Wrong number of dimensions. "
+                f"values.ndim != ndim [{values.ndim} != {ndim}]"
+            )
+        if len(placement) != len(values):
+            raise ValueError(
+                f"Wrong number of items passed {len(values)}, "
+                f"placement implies {len(placement)}"
+            )
+    elif ndim == 2 and len(placement) != 1:
+        # TODO(EA2D): special case unnecessary with 2D EAs
+        raise AssertionError("block.size != values.size")
+
+
+def extract_pandas_array(values, dtype, ndim):
     # Ensure that we don't allow PandasArray / PandasDtype in internals.
     # For now, blocks should be backed by ndarrays when possible.
     if isinstance(values, ABCPandasArray):
@@ -2276,16 +2281,7 @@ def new_block(
     if isinstance(dtype, PandasDtype):
         dtype = dtype.numpy_dtype
 
-    if klass is None:
-        dtype = dtype or values.dtype
-        klass = get_block_type(values, dtype)
-
-    elif klass is DatetimeTZBlock and not is_datetime64tz_dtype(values.dtype):
-        # TODO: This is no longer hit internally; does it need to be retained
-        #  for e.g. pyarrow?
-        values = DatetimeArray._simple_new(values, dtype=dtype)
-
-    return klass(values, ndim=ndim, placement=placement)
+    return values, dtype
 
 
 # -----------------------------------------------------------------

pandas/core/internals/managers.py

@@ -1610,6 +1610,8 @@ def get_slice(self, slobj: slice, axis: int = 0) -> SingleBlockManager:
 
         blk = self._block
         array = blk._slice(slobj)
+        if array.ndim > blk.values.ndim:
+            raise ValueError
         block = blk.make_block_same_class(array, placement=slice(0, len(array)))
         return type(self)(block, self.index[slobj])
 

pandas/tests/indexing/test_indexing.py

@@ -75,7 +75,7 @@ def test_getitem_ndarray_3d(self, index, frame_or_series, indexer_sli):
 
         msgs = []
         if frame_or_series is Series and indexer_sli in [tm.setitem, tm.iloc]:
-            msgs.append(r"Wrong number of dimensions. values.ndim != ndim \[3 != 1\]")
+            msgs.append(r"Wrong number of dimensions. values.ndim > ndim \[3 > 1\]")
         if frame_or_series is Series or indexer_sli is tm.iloc:
             msgs.append(r"Buffer has wrong number of dimensions \(expected 1, got 3\)")
         if indexer_sli is tm.loc or (

pandas/tests/internals/test_internals.py

@@ -1318,17 +1318,19 @@ def test_make_block_no_pandas_array(block_maker):
     assert result.dtype.kind in ["i", "u"]
     assert result.is_extension is False
 
-    # PandasArray, PandasDtype
-    result = block_maker(arr, slice(len(arr)), dtype=arr.dtype, ndim=arr.ndim)
-    assert result.dtype.kind in ["i", "u"]
-    assert result.is_extension is False
-
-    # ndarray, PandasDtype
-    result = block_maker(
-        arr.to_numpy(), slice(len(arr)), dtype=arr.dtype, ndim=arr.ndim
-    )
-    assert result.dtype.kind in ["i", "u"]
-    assert result.is_extension is False
+    if block_maker is make_block:
+        # PandasArray, PandasDtype
+        result = block_maker(arr, slice(len(arr)), dtype=arr.dtype, ndim=arr.ndim)
+        assert result.dtype.kind in ["i", "u"]
+        assert result.is_extension is False
+
+        # new_block no longer taked dtype keyword
+        # ndarray, PandasDtype
+        result = block_maker(
+            arr.to_numpy(), slice(len(arr)), dtype=arr.dtype, ndim=arr.ndim
+        )
+        assert result.dtype.kind in ["i", "u"]
+        assert result.is_extension is False
 
 
 def test_single_block_manager_fastpath_deprecated():