timer using contextmanager

timer.py

# https://docs.python.org/dev/library/contextlib.html#contextlib.ContextDecorator
# http://preshing.com/20110924/timing-your-code-using-pythons-with-statement/
$ python2.7
Python 2.7.6 (default, Nov 26 2013, 12:13:15)
[GCC 4.4.6 20120305 (Red Hat 4.4.6-4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from contextlib import contextmanager
>>> import time
>>> @contextmanager
... def timer():
...     start = time.clock()
...     yield
...     elapsed = time.clock() - start
...     print 'elapsed time {}'.format(elapsed)
...
>>> t = timer()
>>> with t:
...     for i in range(1000000):
...             pass
...
elapsed time 0.12
>>>