Convert numpy array to date list

Question

I have a two-dimensional array of form dates:

[YYY ... ] [MMM ... ] [DDD ... ] [HHH ... ] [MMM ... ] [SSS ... ] 

So it looks like

 data = np.array([ [2015, 2015, 2015, 2015, 2015, 2015], # ... [ 1, 1, 1, 1, 1, 1], [ 1, 1, 1, 2, 2, 2], [ 23, 23, 23, 0, 0, 0], [ 4, 5, 5, 37, 37, 37], [ 59, 1, 2, 25, 27, 29] ]) 

What would be the best way to convert this to a single list of datetime objects?

Answer 1

 import datetime import numpy as np data = np.array( [[2015, 2015, 2015, 2015, 2015, 2015], [ 1, 1, 1, 1, 1, 1], [ 1, 1, 1, 2, 2, 2], [ 23, 23, 23, 0, 0, 0], [ 4, 5, 5, 37, 37, 37], [ 59, 1, 2, 25, 27, 29]] ) # Transpose the data so that columns become rows. data = data.T # A simple list comprehension does the trick, '*' making sure # the values are unpacked for 'datetime.datetime'. new_data = [datetime.datetime(*x) for x in data] print(new_data) 

[datetime.datetime (2015, 1, 1, 23, 4, 59), datetime.datetime (2015, 1, 1, 23, 5, 1), datetime.datetime (2015, 1, 1, 23, 5, 2 ), datetime.datetime (2015, 1, 2, 0, 37, 25), datetime.datetime (2015, 1, 2, 0, 37, 27), datetime.datetime (2015, 1, 2, 0, 37, 29)]

Answer 2

If you want np.datetime64 objects, then this works:

 import functools units = 'YMDhms' first_vals = np.array([1970, 1, 1, 0, 0, 0]) epoch = np.datetime64('1970') results = functools.reduce( np.add, [ d.astype('timedelta64[{}]'.format(unit)) for d, unit in zip(data - first_vals[:,np.newaxis], units) ], epoch ) 

What gives:

 array(['2015-01-01T23:04:59', '2015-01-01T23:05:01', '2015-01-01T23:05:02', '2015-01-02T00:37:25', '2015-01-02T00:37:27', '2015-01-02T00:37:29'], dtype='datetime64[s]')