python练习 多线程

thread.py

from threading import Thread
import time

a = 0

def th1():

    global a
    a = a + 1
    ##print 'a: ', a


def th2():

    global a
    a = a + 1
    ##print 'a: ', a


t1 = Thread(target = th2)
t2 = Thread(target = th1)
t1.start()
print a
t2.start()
print a