timer python generator

This is the easiest way to run some code in a loop with a time-out. When the timeout is reached the loop will stop iterating.

#!/usr/bin/env python


def timer(duration):

    '''This is a generator that stops after the given duration in seconds.
    Through each iteration it yields the time left. If the time left is
    negative then the generator has ended. The amount of negative time left
    represents how long over the duration the generator was when it ended.
    Long over time end results are caused be delays in the outer loop.

    Example, a 3.25 second timer:

        for time_left in timer(3.25):
            print (time_left)
        print ("Finished %f seconds overtime." % (-1 * time_left) )

    '''

    import time
    end_time = time.time() + duration
    time_left = duration
    while time_left > 0.0:
        yield time_left
        time_left = end_time - time.time()
    yield time_left

if __name__ == '__main__':
    import sys
    import time
    for time_left in timer(5):
        sys.stdout.write('\033[1G')  # CHA: cursor to column 1
        sys.stdout.write('%06.4f' % time_left)
        sys.stdout.flush()
        time.sleep(0.1)
    sys.stdout.write('\033[1G')  # CHA: cursor to column 1
    sys.stdout.write('%06.4f' % time_left)
    print ("Finished %f seconds overtime." % (-1 * time_left) )
    sys.stdout.write('\ndone\n')

# vim:set ft=python fileencoding=utf-8 sr et ts=4 sw=4 : See help 'modeline'