python多进程全局共享counter（multiprocessing包实现）
# -*- coding: UTF-8 -*-
from multiprocessing import Pool, Lock, Value
import os
tests_count = 80
lock = Lock()
counter = Value('i', 0) # int type，相当于java里面的原子变量
def run(fn):
global tests_count, lock, counter
with lock:
counter.value += 1
print 'NO. (%d/%d) test start. PID: %d ' %(counter.value, tests_count,os.getpid())
# do something below ...
if __name__ == "__main__":
pool = Pool(10)
# 80个任务，会运行run()80次，每次传入xrange数组一个元素
pool.map(run, xrange(80))
pool.close()
pool.join()
输出：
NO. (1/80) test start. PID: 23785
NO. (2/80) test start. PID: 23785
NO. (3/80) test start. PID: 23786
NO. (5/80) test start. PID: 23786
...
NO. (77/80) test start. PID: 23785
NO. (78/80) test start. PID: 23791
NO. (79/80) test start. PID: 23786
注意事项：
如果使用multiprocessing包，则要按照它的套路走，标准库threading包里面threading.Lock()、acquire()、release()这几个同步方法不生效了，因为Pool是多进程的。上面code可以直接run
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