import time


class Timer(object):
    def __enter__(self):
        self._startTime = time.time()

    def __exit__(self, exc_type, exc_val, exc_tb):
        print ("Elapsed time: {:.9f} sec".format(time.time() - self._startTime))
        
        
# Замерять время так:

with Timer():
	a = 1
    b = a+2