import re, os, time

hz = 250

def get_boot_time():
    f = open('/proc/stat', 'r')
    x = f.readlines()
    f.close()

    re_c = re.compile('^btime (\d+)$')
    for line in x:
        m = re_c.match(line)
        if m:
            return int(m.group(1))
    return None


def get_starttime(pid):
    f = open('/proc/' + str(pid) + '/stat', 'r')
    x = f.read().split(' ')
    f.close()
    # starttime
    return int(x[21].strip())

print time.time()
print get_boot_time()
print get_starttime(os.getpid())/hz

# running [s]
print time.time() - (get_boot_time() + get_starttime(os.getpid())/hz)
~