DOC: Inconsistencies in converting array with datetime values into object array #19782
Description
When converting a datetime64[ns] array into object type, it returns the date as an integer instead of datetime.datetime object
Reproducing code example:
>>> import numpy as np
>>> from datetime import datetime
>>> d = datetime.now()
>>> np.array(d)
array(datetime.datetime(2021, 8, 29, 20, 1, 32, 350877), dtype=object)
>>> np.array(d, dtype="datetime64[ns]")
array('2021-08-29T20:01:32.350877000', dtype='datetime64[ns]')
>>> np.array(d).astype("O") # Keeps the same, as expected
array(datetime.datetime(2021, 8, 29, 20, 1, 32, 350877), dtype=object)
>>> np.array(d, dtype="datetime64[ns]").astype("O") # Transforms to int. Unexpected
array(1630267292350877000, dtype=object)
>>> np.array(d, dtype="datetime64[ns]").view(np.int64) # Transforms to int. Expected
array(1630267292350877000)IMO, the results from np.array(d).astype("O") and np.array(d, dtype="datetime64[ns]").astype("O") should be equal
NumPy/Python version information:
1.18.5 3.8.3 (default, Jul 2 2020, 11:26:31)
[Clang 10.0.0 ]