Context manager for timing code execution.

stopwatch.py

import time
import sys
from contextlib import contextmanager


@contextmanager
def stopwatch(label, width=20):
    '''
    A context manager that prints out the execution time of the nested code.
    '''

    plat = sys.platform.rstrip('0123456789')
    time_fn = time.clock if plat == 'win' else time.time
    
    start = time_fn()
    try:
        yield
    finally:
        print '{:<{w}}: {}'.format(label, time_fn() - start, w=width)