说明
相应的学习视频见链接,本文只对重点进行总结。
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
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
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)
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)
#下面代码在没有lock锁时,会卖出0票,加上lock就正常
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)
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
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