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服务器之家 - 脚本之家 - Python - 手把手带你了解python多进程,多线程

手把手带你了解python多进程,多线程

2021-12-22 00:37Mr DaYang Python

这篇文章主要介绍了python多线程与多进程及其区别详解,文中通过示例代码介绍的非常详细,对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下

说明

相应的学习视频见链接,本文只对重点进行总结。

手把手带你了解python多进程,多线程

手把手带你了解python多进程,多线程

多进程

重点(只要看下面代码的main函数即可)

1.创建

2.如何开守护进程

3.多进程,开销大,用for循环调用多个进程时,后台cpu一下就上去了

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import time
import multiprocessing
import os
def dance(who,num):
    print("dance父进程:{}".format(os.getppid()))
    for i in range(1,num+1):
        print("进行编号:{}————{}跳舞。。。{}".format(os.getpid(),who,i))
        time.sleep(0.5)
def sing(num):
    print("sing父进程:{}".format(os.getppid()))
    for i in range(1,num+1):
        print("进行编号:{}----唱歌。。。{}".format(os.getpid(),i))
        time.sleep(0.5)
def work():
    for i in range(10):
        print("工作中。。。")
        time.sleep(0.2)
if __name__ == '__main__':
    # print("main主进程{}".format(os.getpid()))
    start= time.time()
    #1 进程的创建与启动
    # # 1.1创建进程对象,注意dance不能加括号
    # # dance_process = multiprocessing.process(target=dance)#1.无参数
    # dance_process=multiprocessing.process(target=dance,args=("lin",3))#2.以args=元祖方式
    # sing_process = multiprocessing.process(target=sing,kwargs={"num":3})#3.以kwargs={}字典方式
    # # 1.2启动进程
    # dance_process.start()
    # sing_process.start()
    #2.默认-主进程和子进程是分开的,主进程只要1s就可以完成,子进程要2s,主进程会等所有子进程执行完,再退出
    # 2.1子守护主进程,当主一但完成,子就断开(如qq一关闭,所有聊天窗口就没了).daemon=true
    work_process = multiprocessing.process(target=work,daemon=true)
    work_process.start()
    time.sleep(1)
    print("主进程完成了!")#主进程和子进程是分开的,主进程只要1s就可以完成,子进程要2s,主进程会等所有子进程执行完,再退出
    print("main主进程花费时长:",time.time()-start)
    #

多线程

手把手带你了解python多进程,多线程

重点

1.创建

2.守护线程

3.线程安全问题(多人抢票,会抢到同一张)

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import time
import os
import threading
def dance(num):
    for i in range(num):
        print("进程编号:{},线程编号:{}————跳舞。。。".format(os.getpid(),threading.current_thread()))
        time.sleep(1)
def sing(count):
    for i in range(count):
        print("进程编号:{},线程编号:{}----唱歌。。。".format(os.getpid(),threading.current_thread()))
        time.sleep(1)
def task():
    time.sleep(1)
    thread=threading.current_thread()
    print(thread)
if __name__ == '__main__':
    # start=time.time()
    # # sing_thread =threading.thread(target=dance,args=(3,),daemon=true)#设置成守护主线程
    # sing_thread = threading.thread(target=dance, args=(3,))
    # dance_thread = threading.thread(target=sing,kwargs={"count":3})
    #
    # sing_thread.start()
    # dance_thread.start()
    #
    # time.sleep(1)
    # print("进程编号:{}主线程结束...用时{}".format(os.getpid(),(time.time()-start)))
    for i in range(10):#多线程之间执行是无序的,由cpu调度
        sub_thread = threading.thread(target=task)
        sub_thread.start()

线程安全

由于线程直接是无序进行的,且他们共享同一个进程的全部资源,所以会产生线程安全问题(比如多人在线抢票,买到同一张)

手把手带你了解python多进程,多线程
手把手带你了解python多进程,多线程

#下面代码在没有lock锁时,会卖出0票,加上lock就正常

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import threading
import time
lock =threading.lock()
class sum_tickets:
    def __init__(self,tickets):
        self.tickets=tickets
def window(sum_tickets):
    while true:
        with lock:
            if sum_tickets.tickets>0:
                time.sleep(0.2)
                print(threading.current_thread().name,"取票{}".format(sum_tickets.tickets))
                sum_tickets.tickets-=1
            else:
                break
if __name__ == '__main__':
    sum_tickets=sum_tickets(10)
    sub_thread1 = threading.thread(name="窗口1",target=window,args=(sum_tickets,))
    sub_thread2 = threading.thread(name="窗口2",target=window,args=(sum_tickets,))
    sub_thread1.start()
    sub_thread2.start()

高并发拷贝(多进程,多线程)

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import os
import multiprocessing
import threading
import time
def copy_file(file_name,source_dir,dest_dir):
    source_path = source_dir+"/"+file_name
    dest_path =dest_dir+"/"+file_name
    print("当前进程为:{}".format(os.getpid()))
    with open(source_path,"rb") as source_file:
        with open(dest_path,"wb") as dest_file:
            while true:
                data=source_file.read(1024)
                if data:
                    dest_file.write(data)
                else:
                    break
    pass
if __name__ == '__main__':
    source_dir=r'c:\users\administrator\desktop\注意力'
    dest_dir=r'c:\users\administrator\desktop\test'
    start = time.time()
    try:
        os.mkdir(dest_dir)
    except:
        print("目标文件已存在")
    file_list =os.listdir(source_dir)
    count=0
    #1多进程
    for file_name in file_list:
        count+=1
        print(count)
        sub_processor=multiprocessing.process(target=copy_file,
                                args=(file_name,source_dir,dest_dir))
        sub_processor.start()
        # time.sleep(20)
    print(time.time()-start)
#这里有主进程和子进程,通过打印可以看出,主进程在创建1,2,3,4,,,21过程中,子进程已有的开始执行,也就是说,每个进程是互不影响的
# 9
# 10
# 11
# 12
# 13
# 当前进程为:2936(当主进程创建第13个时,此时,第一个子进程开始工作)
# 14
# 当前进程为:10120
# 当前进程为:10440
# 15
# 当前进程为:9508
    # 2多线程
    # for file_name in file_list:
    #     count += 1
    #     print(count)
    #     sub_thread = threading.thread(target=copy_file,
    #                                             args=(file_name, source_dir, dest_dir))
    #     sub_thread.start()
    #     # time.sleep(20)
    # print(time.time() - start)

总结

本篇文章就到这里了,希望能给你带来帮助,也希望您能够多多关注服务器之家的更多内容!

原文链接:https://blog.csdn.net/m0_46204224/article/details/119737937

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