Converting numpy datetime64 to long integer and back

Question

How to convert NumPy datetime64 to a long ineteger and back?

import numpy as np
import datetime

np.datetime64(datetime.datetime.now()).astype(long)

Gives a value of 1511975032478959

np.datetime64(np.datetime64(datetime.datetime.now()).astype(long))

Gives an error:

ValueError: Converting an integer to a NumPy datetime requires a specified unit

Answer 1

You need to specify the units of the long int (in this case, microseconds).

 np.datetime64(np.datetime64(datetime.datetime.now()).astype(long), 'us')

returns

 numpy.datetime64('2017-11-29T17:11:44.638713')

Answer 2

'us' converts to microseconds. If you require a different format use:

as shown here