Python 进程学习笔记

1.进程的创建

import multiprocessing

def func(msg):
    print(msg)
    print('This is a processing')

if __name__ == '__main__':
    p = multiprocessing.Process(target=func,args=('test',))
    p.start()

2.进程的并行

import multiprocessing

def func(msg):
    print(msg)
    print('This is a processing')

if __name__ == '__main__':
    p1 = multiprocessing.Process(target=func,args=('test1',))
    p2 = multiprocessing.Process(target=func,args=('test2',))
    p1.start()
    p2.start()
    p1.join()
    p2.join()

3.进程锁的两种使用方法

import multiprocessing
from datetime import datetime,timedelta

#with用锁
def func2(lock,f):
    with lock:
        print(datetime.now())

#lock.acquire()用锁
def func1(lock,f):
    lock.acquire()
    
    print(datetime.now())

    lock.release

if __name__ == '__main__':
    lock = multiprocessing.Lock()
    f = 'file.txt'
    p1 = multiprocessing.Process(target=func2,args=(lock,f))
    p2 = multiprocessing.Process(target=func1,args=(lock,f))
    p1.start()
    p2.start()
    p1.join()
    p2.join()

3.设置资源的访问数量

import multiprocessing
from datetime import datetime,timedelta

#with用锁
def func2(s,lock,f):
    with s:
        with lock:
            print(func2.__name__ +' ' +datetime.now().strftime('%Y-%m-%d %H-%S-%M'))

#lock.acquire()用所
def func1(lock,f):
    lock.acquire()

    print(func1.__name__ +' ' + datetime.now().strftime('%Y-%m-%d %H-%S-%M'))

    lock.release

if __name__ == '__main__':
    s = multiprocessing.Semaphore(2) # 设置只能访问两次
    for i in range(5):
        lock = multiprocessing.Lock()
        f = 'file.txt'
        p1 = multiprocessing.Process(target=func2,args=(s,lock,f))
        p2 = multiprocessing.Process(target=func1,args=(lock,f))
        p1.start()
        p2.start()
        p1.join()
        p2.join()

4.Processing 队列设置

import multiprocessing

def write(q):
    q.put('Hello,World')

def read(q):
    print(q.get())


if __name__ == '__main__':
    q = multiprocessing.Queue()
    qwriter = multiprocessing.Process(target=write,args=(q,))
    qreader = multiprocessing.Process(target=read,args=(q,))
    qwriter.start()
    qreader.start()

5.管道pipe

pipe返回（conn1，conn2）代表管道的两端，可以用[0]、[1]调用；

duplex参数如果设为True，则conn1和conn2都可以收发；

duplex参数如果设为False，则conn1负责接收，conn2负责发送。

import multiprocessing

def sender(p):
   p.send("hello world")

def receiver(p):
    print(p.recv())

if __name__ == "__main__":
    p = multiprocessing.Pipe()
    psender=multiprocessing.Process(target=sender,args=(p[0],))
    preceiver = multiprocessing.Process(target=receiver, args=(p[1],))
    psender.start()
    preceiver.start()

6.进程之间manager

manager实现进程之间数据共享

import multiprocessing

def func(list1,d,i):
    list1[i] = i
    d['a'] = i

if __name__ == "__main__":
    with multiprocessing.Manager() as manager:
        list1 = manager.list(range(5,10))
        d = manager.dict()
        plist = []
        for i in range(5):
            p = multiprocessing.Process(target=func,args=(list1,d,i))
            plist.append(p)
            p.start()
            p.join()
        for i in plist:
            print(i)
        print(d)
        print(list1)