Python多进程数据共享

import multiprocessing
x = 0
lock = multiprocessing.Lock()
def main():
    global x
    lock.acquire()
    x += 1
    lock.release()
if __name__ == '__main__':
    pool = multiprocessing.Pool(4)
    for i in range(4):
        pool.apply_async(main)
    pool.close()
    pool.join()
    print(x)   # 输出0 并未对数据进行更改
    print("end")

import multiprocessing
def main(num):
    num.value += 1
if __name__ == '__main__':
    num = multiprocessing.Value("d", 10.0)
    pool = multiprocessing.Pool(4)
    for i in range(4):
        pool.apply_async(main, args=(num,))
    pool.close()
    pool.join()
    print(num.value) # 值仍为10.0，并未改变
    print("end")  

import multiprocessing
def main(v):
    v.value += 1
if __name__ == '__main__':
    value = multiprocessing.Value("d", 10.0)
    jobs = [multiprocessing.Process(target=main, args=(value,)) for i in range(10)]
    for j in jobs:
        j.start()
    for j in jobs:
        j.join()
    print('Results:', value.value)  # result 20.0 修改成功