python之multiprocessing

创建单个进程示例：

from multiprocessing import Process
import time


def add(a, b):
    print("starting to job")
    print(a + b)
    time.sleep(1)
    print("stoping to job")


if __name__ == '__main__':
    time1 = time.time()
    # 创建进程
    p1 = Process(target=add, args=(1, 2))
    # 启动进程
    p1.start()
    # 连接进程
    p1.join()
    time2 = time.time()
    print("执行程序花费时长:{}".format(time2-time1))

使用for循环创建多个进程：

import time
from multiprocessing import Process


def sleep():
    print("starting to sleep")
    time.sleep(1)
    print("stoping to sleep")


if __name__ == '__main__':
    time1 = time.time()
    process_list = list()
    for i in range(10):
        p = Process(target=sleep)
        p.start()
        process_list.append(p)
    for p in process_list:
        p.join()
    time2 = time.time()
    print("程序执行时间为:{}".format(time2-time1))

线程池示例：

from multiprocessing import Pool


def number(num):
    print("worker %d" % num)


if __name__ == '__main__':
    # 创建线程池
    pool = Pool(4)
    # 启动线程池中的进程
    pool.map(number, range(5))
    # 关闭进程池
    pool.close()
    pool.join()

队列示例：

from multiprocessing import Queue


def add(q, x, y):
    result = x + y
    q.put(result)


def get_result(q):
    while True:
        d = q.get()
        if d is None:
            break
        print(d)


if __name__ == '__main__':
    # 创建队列
    q = Queue()
    p1 = Process(target=add, args=(q, 1, 4))
    p2 = Process(target=get_result, args=(q,))
    p1.start()
    p2.start()
    p1.join()
    # 发送结束信号
    q.put(None)
    p2.join()

管道示例：

from multiprocessing import Pipe


def send_message(conn):
    for i in range(5):
        conn.send(i)
    conn.close()


def get_message(conn):
    while True:
        msg = conn.recv()
        if msg is None:
            break
        print(msg)


if __name__ == '__main__':
    # 创建管道
    conn1, conn2 = Pipe()
    p1 = Process(target=send_message, args=(conn1,))
    p2 = Process(target=get_message, args=(conn2,))
    p1.start()
    p2.start()
    p1.join()
    # 发送结束信号
    conn1.send(None)
    p2.join()

共享内存 Value示例：

from multiprocessing import Value


def job1(n):
    n.value += 1
    print('job1:', n.value)


def job2(n):
    n.value -= 1
    print('job2:', n.value)


if __name__ == '__main__':
    n = Value('i', 5)
    p1 = Process(target=job1, args=(n,))
    p2 = Process(target=job2, args=(n,))
    p1.start()
    p2.start()
    p1.join()
    p2.join()

共享内存 Array示例：

from multiprocessing import Array


def job1(n):
    for i in n:
        print("job1:", i)


def job2(n):
    p = n[3]
    print("job2:", p)


if __name__ == '__main__':
    n = Array("i", [5, 4, 3, 2, 1])
    p1 = Process(target=job1, args=(n,))
    p2 = Process(target=job2, args=(n,))
    p1.start()
    p2.start()
    p1.join()
    p2.join()

进程锁示例：

from multiprocessing import Lock


def job1(l, i):
    l.acquire()
    try:
        print("hello world", i)
    except:
        l.release()
        pass


if __name__ == '__main__':
    process_list = list()
    l = Lock()
    for i in range(6):
        p1 = Process(target=job1, args=(l, i,))
        p1.start()
        process_list.append(p1)
    for p in process_list:
        p.join()