REF: avoid ravel in ints_to_pytimedelta

pandas/_libs/tslibs/timedeltas.pyx

@@ -161,42 +161,61 @@ def ints_to_pytimedelta(ndarray m8values, box=False):
         array of Timedelta or timedeltas objects
     """
     cdef:
+        NPY_DATETIMEUNIT reso = get_unit_from_dtype(m8values.dtype)
         Py_ssize_t i, n = m8values.size
         int64_t value
-        object[::1] result = np.empty(n, dtype=object)
-        NPY_DATETIMEUNIT reso = get_unit_from_dtype(m8values.dtype)
+        object res_val
+
+        # Note that `result` (and thus `result_flat`) is C-order and
+        #  `it` iterates C-order as well, so the iteration matches
+        #  See discussion at
+        #  github.com/pandas-dev/pandas/pull/46886#discussion_r860261305
+        ndarray result = cnp.PyArray_EMPTY(m8values.ndim, m8values.shape, cnp.NPY_OBJECT, 0)
+        object[::1] res_flat = result.ravel()     # should NOT be a copy
 
-    arr = m8values.view("i8")
+        ndarray arr = m8values.view("i8")
+        cnp.flatiter it = cnp.PyArray_IterNew(arr)
 
     for i in range(n):
+        # Analogous to: value = arr[i]
+        value = (<int64_t*>cnp.PyArray_ITER_DATA(it))[0]
 
-        value = arr[i]
         if value == NPY_NAT:
-            result[i] = <object>NaT
+            res_val = <object>NaT
         else:
             if box:
-                result[i] = _timedelta_from_value_and_reso(value, reso=reso)
+                res_val = _timedelta_from_value_and_reso(value, reso=reso)
             elif reso == NPY_DATETIMEUNIT.NPY_FR_ns:
-                result[i] = timedelta(microseconds=int(value) / 1000)
+                res_val = timedelta(microseconds=int(value) / 1000)
             elif reso == NPY_DATETIMEUNIT.NPY_FR_us:
-                result[i] = timedelta(microseconds=value)
+                res_val = timedelta(microseconds=value)
             elif reso == NPY_DATETIMEUNIT.NPY_FR_ms:
-                result[i] = timedelta(milliseconds=value)
+                res_val = timedelta(milliseconds=value)
             elif reso == NPY_DATETIMEUNIT.NPY_FR_s:
-                result[i] = timedelta(seconds=value)
+                res_val = timedelta(seconds=value)
             elif reso == NPY_DATETIMEUNIT.NPY_FR_m:
-                result[i] = timedelta(minutes=value)
+                res_val = timedelta(minutes=value)
             elif reso == NPY_DATETIMEUNIT.NPY_FR_h:
-                result[i] = timedelta(hours=value)
+                res_val = timedelta(hours=value)
             elif reso == NPY_DATETIMEUNIT.NPY_FR_D:
-                result[i] = timedelta(days=value)
+                res_val = timedelta(days=value)
             elif reso == NPY_DATETIMEUNIT.NPY_FR_W:
-                result[i] = timedelta(weeks=value)
+                res_val = timedelta(weeks=value)
             else:
                 # Month, Year, NPY_FR_GENERIC, pico, fempto, atto
                 raise NotImplementedError(reso)
 
-    return result.base  # .base to access underlying np.ndarray
+        # Note: we can index result directly instead of using PyArray_MultiIter_DATA
+        #  like we do for the other functions because result is known C-contiguous
+        #  and is the first argument to PyArray_MultiIterNew2.  The usual pattern
+        #  does not seem to work with object dtype.
+        #  See discussion at
+        #  github.com/pandas-dev/pandas/pull/46886#discussion_r860261305
+        res_flat[i] = res_val
+
+        cnp.PyArray_ITER_NEXT(it)
+
+    return result
 
 
 # ----------------------------------------------------------------------

pandas/core/arrays/datetimelike.py

@@ -437,9 +437,7 @@ def astype(self, dtype, copy: bool = True):
                 return converted.reshape(self.shape)
 
             elif self.dtype.kind == "m":
-                i8data = self.asi8.ravel()
-                converted = ints_to_pytimedelta(self._ndarray.ravel(), box=True)
-                return converted.reshape(self.shape)
+                return ints_to_pytimedelta(self._ndarray, box=True)
 
             return self._box_values(self.asi8.ravel()).reshape(self.shape)