#1 进程的开销大于线程 # from threading import Thread # import time # # def task(name): #     print('%s is running'%name) #     time.sleep(3) #     print('%s is done'%name) # # if __name__ == '__main__': #     t=Thread(target=task,args=('alex',))           #元祖形式 #     t.start() #     print('主线程')         #alex is running 主进程 几乎是同时打印 # from multiprocessing import Process # import time # # def task(name): #     print('%s is running'%name) #     time.sleep(3) #     print('%s is done'%name) # # if __name__ == '__main__': #     t=Process(target=task,args=('alex',))           #元祖形式 #     t.start() #     print('主进程')   #一定是先打印主进程  因为他要申请内存空间 将开启进程的信号发给操作系统后，操作系统要申请内存空间，让好拷贝父进程地址空间到子进程，开销远大于线程 #2同一进程内的多个线程共享进程的地址空间 ''' from multiprocessing import Process import os def work():     global n     n=0 if __name__ == '__main__':     n=100     p=Process(target=work)     p.start()     p.join()     print('主',n) from threading import Thread import os def work():     global n     n=0 if __name__ == '__main__':     n=100     t=Thread(target=work)     t.start()     t.join()     print('主线程',n) ''' #3 pid # from multiprocessing import Process # import os # # def work(): #     print('hello',os.getpid()) # # if __name__ == '__main__': #     p1=Process(target=work) #     p2=Process(target=work) #     p1.start() #     p2.start() #     print('主进程',os.getpid()) from threading import Thread import os def work():     print('hello',os.getpid()) if __name__ == '__main__':     t1=Thread(target=work)     t1.start()     print('主线程pid',os.getpid())