python3.3 threading

import threading
import time

def f(t_time):
    end = time.time() + t_time
    i = 0
    while time.time() < end:
        i = i + 1
    print(end)

tl = []
for row in [3, 6]:
    t = threading.Thread(target=f, args=(row,))
    tl.append(t)

for row in tl:
    row.start()
for row in tl:
    row.join()