this method uses numpy vectorized function, which is slightly faster than using a list generator

date strings list to python datetime objects

import numpy as np
import datetime
def datestr_to_datetime(x):
    return datetime.datetime.strptime(x,'%Y-%m-%dT%H:%M:%SZ')

# where dates is some list of dates as a string... 
# vectorize the function
converttime = np.vectorize(datestr_to_datetime)
DATES = converttime(dates)