Using a Python context manager as timer.

timer.py

import time

class Timer:

    def __enter__(self):
        self.__start = time.time()


    def __exit__(self, exType, exValue, exTraceback):
        self.__elapsed = time.time() - self.__start


    @property
    def elapsed(self):
        return self.__elapsed


timer = Timer()

with timer:
    time.sleep(2)

print("elapsed time:", timer.elapsed)

Nice :)
Added additional sleeps for further demonstration:

import time

class Timer:

    def __enter__(self):
        self.__start = time.time()


    def __exit__(self, exType, exValue, exTraceback):
        self.__elapsed = time.time() - self.__start


    @property
    def elapsed(self):
        return self.__elapsed


timer = Timer()

time.sleep(1)

with timer:
    time.sleep(2)

time.sleep(1)

print("elapsed time:", timer.elapsed)

$ python timer.py 
elapsed time: 2.001952489954798