进程相关操作

python中的多线程无法利用多核优势，如果想要充分地使用多核CPU的资源（os.cpu_count()查看），在python中大部分情况需要使用多进程。

Python提供了multiprocessing。multiprocessing模块用来开启子进程，并在子进程中执行我们定制的任务（比如函数），该模块与多线程模块threading的编程接口类似。

 

简单的进程程序:

import multiprocessing  #引入模块
def task(arg):
    print(arg)

def run():
    for i in range(10):#循环创建十个进程　　
　　　　 p=multiprocessing.Process(target=task,args=(i,))
        p.start() #准备好执行进程
if __name__=="__main__":
    run()

常用功能:

join():括号内有参数时,指定等待子进程的时间,时间到了以后继续向下执行,无参数时,等待子进程执行完毕以后继续向下执行.

daemon():括号内默认值是False,手动改成True后,优先执行主进程,执行完不等待子进程是否已经执行完.

name():创建进程名称   name=multiprocessing.current_process()#获取线程名字

 

创建进程(两种方式):

1 类继承方法创建:

import multiprocessing
class MyProcess(multiprocessing.Process):
    def run(self):
        print("当前进程是:",multiprocessing.current_process())

def run():
    p1=MyProcess()#进程一
    p1.start()  #自动执行类里面的run方法
    p2=MyProcess()
    p2.start()#进程二

if __name__=="__main__":
    run()

2普通方法

import multiprocessing

def task():
    print("当前进程是:",multiprocessing.current_process())

def run():
    for i in range(2):
        p=multiprocessing.Process(target=task,)
        p.start()

if __name__=="__main__":
    run()

 

数据共享:

1 Queue:

import multiprocessing
def task(arg,q):
    q.put(arg)
if __name__=="__main__":
    q = multiprocessing.Queue()
    for i in range(10):
        p = multiprocessing.Process(target=task,args=(i,q,))
        p.start()
    while True:
        v = q.get()
        print(v)

import mulprocessing
q = multiprocessing.Queue()

    def task(arg,q):
    q.put(arg)

def run():
    for i in range(10):
        p = multiprocessing.Process(target=task, args=(i, q,))
    p.start()

    while True:
    v = q.get()
    print(v)

run()

2 Manger:

import multiprocessing
import time
def func(arg,dic):
    time.sleep(2)
    dic[arg] = 100


if __name__ == "__main__":
    m = multiprocessing.Manager()
    dic = m.dict()

    process_list = []
    for i in range(10):
        p = multiprocessing.Process(target=func, args=(i, dic,))
        p.start()

        process_list.append(p)

    while True:
        count=0
        for p in process_list:
            if not p.is_alive():
                count+=1
        if count==len(process_list):
            break
    print(dic)

 

进程锁:与线程用法一致.

import time
import multiprocessing


lock = multiprocessing.RLock()

def task(arg):
    print('鬼子来了')
    lock.acquire()
    time.sleep(2)
    print(arg)
    lock.release()


if __name__ == '__main__':
    p1 = multiprocessing.Process(target=task,args=(1,))
    p1.start()

    p2 = multiprocessing.Process(target=task, args=(2,))
    p2.start()

 

进程池:限制进程最多创建的数

import multiprocessing
from concurrent.futures import ProcessPoolExecutor

def task():
    print("当前进程是:",multiprocessing.current_process())
    time.sleep(1)

if __name__=="__main__":
    pool=ProcessPoolExecutor(5)
    for i in range(10):
        pool.submit(task,)


打印结果为:
当前进程是: <Process(Process-2, started)>
当前进程是: <Process(Process-3, started)>
当前进程是: <Process(Process-4, started)>
当前进程是: <Process(Process-1, started)>
当前进程是: <Process(Process-5, started)>
一秒钟以后:
当前进程是: <Process(Process-2, started)>
当前进程是: <Process(Process-3, started)>
当前进程是: <Process(Process-4, started)>
当前进程是: <Process(Process-1, started)>
当前进程是: <Process(Process-5, started)>

 

简单爬虫:

import requests
from bs4 import BeautifulSoup
from concurrent.futures import ProcessPoolExecutor,ThreadPoolExecutor

def task(url):
    print(url)
    r1=requests.get(url=url,headers={ 'User-Agent':'Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.92 Safari/537.36'
         })

    #查看下载下来的文本信息
    soup=BeautifulSoup(r1.text,'html.parser')
    print(soup.text)
    # content_list=soup.find('div',attrs={'id':content_list})
    # for item in content_list.find_all('div',attr={'class':'item'})
    #       title = item.find('a').text.strip()
    #       target_url = item.find('a').get('href')
    #       print(title,target_url)

def run():
    pool=ThreadPoolExecutor(5)
    for i in range(1,50):
        pool.submit(task,'https://dig.chouti.com/all/hot/recent/%s'%i)