python多进程多线程

Posted 2020-11-22 chenjie0818

一：多线程和多进程

进程是多个资源的集合。

线程是就是进程里面具体干活的。

线程和线程之间是互相独立的。

二：多线程使用threading模块

启用多线程：

import threading

def down_load():
    time.sleep(5)
    print("运行完了")

t = threading.Thread(target=down_load,args=(‘name‘,‘abfd‘))   #生成一个线程实例

t.start 启动线程
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线程等待：

import threading
import time

def down_load():
    time.sleep(5)
    print("运行完了")

start_time = time.time()
for i in range(5):
    t = threading.Thread(target=down_load)
    t.start()

while threading.activeCount()!=1:
    pass

print(threading.activeCount()) #查看当前线程数
print(threading.current_thread())#查看当前线程

end_time = time.time()
print(end_time - start_time)
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下载图片：

import requests,time,threading
from hashlib import md5

result_list = {}
def down_load_pic(url):    #下载图片的函数
    req = requests.get(url)
    m = md5(url.encode())
    file_name = m.hexdigest()+‘.png‘
    with open(file_name ,‘wb‘) as fw:
        fw.write(req.content)
    result_list[file_name] = threading.current_thread()

url_list = [‘http://www.nnzhp.cn/wp-content/uploads/2019/10/f410afea8b23fa401505a1449a41a133.png‘,
            ‘http://www.nnzhp.cn/wp-content/uploads/2019/11/481b5135e75c764b32b224c5650a8df5.png‘,
            ‘http://www.nnzhp.cn/wp-content/uploads/2019/11/b23755cdea210cfec903333c5cce6895.png‘,
            ‘http://www.nnzhp.cn/wp-content/uploads/2019/11/542824dde1dbd29ec61ad5ea867ef245.png‘]

start_time = time.time()
for url in url_list:
    t = threading.Thread(target=down_load_pic,args=(url,))
    t.start()

while threading.activeCount()!=1:
    pass

end_time = time.time()
print(end_time - start_time)
print(result_list)
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异步任务，发送邮件：

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import yagmail,threading

def send_mail():    #发送邮件函数
    smtp = yagmail.SMTP(host=‘smtp.163.com‘,
                        user=‘[e-mail]‘,
                        password=‘xxxxxx‘
                        )
    smtp.send(to=‘[e-mail]‘,cc=[‘[e-mail]‘,‘[e-mail]‘],subject=‘标题‘,
              contents=‘正文‘,attachments=[r‘/Users/xxx.py‘]
              )

def async_send_mail():    #通过线程发送邮件
    t = threading.Thread(target=send_mail)
    t.start()

线程池，导入threadpool：

import threadpool
import requests,time,threading
from hashlib import md5

def down_load_pic(url):  #下载图片函数
    print(threading.current_thread())
    req = requests.get(url)
    m = md5(url.encode())
    with open( m.hexdigest()+‘.png‘,‘wb‘) as fw:
        fw.write(req.content)

url_list = [‘http://www.nnzhp.cn/wp-content/uploads/2019/10/f410afea8b23fa401505a1449a41a133.png‘,
            ‘http://www.nnzhp.cn/wp-content/uploads/2019/11/481b5135e75c764b32b224c5650a8df5.png‘,
            ‘http://www.nnzhp.cn/wp-content/uploads/2019/11/b23755cdea210cfec903333c5cce6895.png‘,
            ‘http://www.nnzhp.cn/wp-content/uploads/2019/11/542824dde1dbd29ec61ad5ea867ef245.png‘]

pool = threadpool.ThreadPool(20)  #实例化一个线程池
reqs = threadpool.makeRequests(down_load_pic,url_list)  #分配数据
[pool.putRequest(req) for req in reqs]  #列表生成式
print(threading.activeCount())
pool.wait() #等待
print(‘end‘)

守护线程：

#主线程结束，守护线程立马死掉。比如浏览器下打开多个窗口，一旦关闭浏览器，下面所有窗口全部关闭
import threading,time

def down_load():
    time.sleep(5)
    print("运行完了")

for i in range(10):
    t = threading.Thread(target=down_load)
    t.setDaemon(True) #设置子线程为守护线程
    t.start()

print(‘over‘)

线程锁：

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#多个线程操作同一个数据的时候，就得加锁
import threading

num = 0

lock = threading.Lock() #申请一把锁

def add():
    global num
    # lock.acquire()#加锁
    # num+=1
    # lock.release()#解锁  #死锁
    with lock:#简写，用with也会帮你加锁，解锁
        num+=1

for i in range(20):
    t = threading.Thread(target=add,)
    t.start()

while threading.activeCount() !=1:
    pass

print(num)

多进程，导入multiprocessing模块：

import multiprocessing,time
def down_load():
    time.sleep(5)
    print("运行完了")

if __name__ == ‘__main__‘:
    for i in range(5):
        p = multiprocessing.Process(target=down_load)
        p.start()

    while len(multiprocessing.active_children())!=0:#等待子进程结束
        pass

    print(multiprocessing.current_process())

    print(‘end‘)