Python get structed time string

datetime_struct.py

import datetime
import time

#Get now time string
timestr = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")

#Calc time delta
t1 = datetime.datetime.now()
time.sleep(3)
t2 = datetime.datetime.now()
timedelta_str = str(t2-t1)

#Get datetime from a string and compare two datetime
t3 = datetime.datetime.strptime("2016-03-16 09:01:02","%Y-%m-%d %H:%M:%S")
t4 = datetime.datetime.strptime("2016-03-15 18:03:27","%Y-%m-%d %H:%M:%S")
result = t3<t4 #False