REF: handle ravel inside astype_nansafe (#38507)

Author: jbrockmendel

pandas/core/dtypes/cast.py

@@ -973,6 +973,14 @@ def astype_nansafe(
     ValueError
         The dtype was a datetime64/timedelta64 dtype, but it had no unit.
     """
+    if arr.ndim > 1:
+        # Make sure we are doing non-copy ravel and reshape.
+        flags = arr.flags
+        flat = arr.ravel("K")
+        result = astype_nansafe(flat, dtype, copy=copy, skipna=skipna)
+        order = "F" if flags.f_contiguous else "C"
+        return result.reshape(arr.shape, order=order)
+
     # dispatch on extension dtype if needed
     if isinstance(dtype, ExtensionDtype):
         return dtype.construct_array_type()._from_sequence(arr, dtype=dtype, copy=copy)

pandas/core/internals/blocks.py

@@ -629,10 +629,6 @@ def astype(self, dtype, copy: bool = False, errors: str = "raise"):
             else:
                 raise
 
-        if isinstance(new_values, np.ndarray):
-            # TODO(EA2D): special case not needed with 2D EAs
-            new_values = new_values.reshape(self.shape)
-
         newb = self.make_block(new_values)
         if newb.is_numeric and self.is_numeric:
             if newb.shape != self.shape:
@@ -691,9 +687,7 @@ def _astype(self, dtype: DtypeObj, copy: bool) -> ArrayLike:
                 # We still need to go through astype_nansafe for
                 #  e.g. dtype = Sparse[object, 0]
 
-            # astype_nansafe works with 1-d only
-            vals1d = values.ravel()
-            values = astype_nansafe(vals1d, dtype, copy=True)
+            values = astype_nansafe(values, dtype, copy=True)
 
         return values