Question

In Numpy, I am trying to get the time of day for each element in an array of datatime64.

I could settle for a new array of timedelta64 which contains the time passed since the beginning of day for each element.

I already tried using numpy.datetime_as_string, but I don’t know how to manipulate the string.

Answer 1

def datetime64_to_time_of_day(datetime64_array):
    """
    Return a new array. For every element in datetime64_array return the time of day (since midnight).
    >>> datetime64_to_time_of_day(np.array(['2012-01-02T01:01:01.001Z'],dtype='datetime64[ms]'))
    array([3661001], dtype='timedelta64[ms]')
    >>> datetime64_to_time_of_day(np.datetime64('2012-01-02T01:01:01.001Z','[ms]'))
    numpy.timedelta64(3661001,'ms')
    """
    day = datetime64_array.astype('datetime64[D]').astype(datetime64_array.dtype)
    time_of_day = datetime64_array - day
    return time_of_day