Measure time between pressing 'space' key twice.

time_space.py

import sys
import termios
import time
import tty

def wait_space():
    if sys.stdin.read(1) == ' ':
        return time.time()
    return wait_space()

def measure():
    fd = sys.stdin.fileno()
    attrs = termios.tcgetattr(fd)
    print "Press space twice."
    try:
        tty.setraw(sys.stdin.fileno())
        start = wait_space()
        delta = wait_space() - start
    finally:
        termios.tcsetattr(fd, termios.TCSADRAIN, attrs)
    print "Time between presses: %0.04fs" % delta

if __name__ == '__main__':
    measure()