进程与线程的区别

1、开进程的开销远大于开线程，开启进程需要单独申请内存空间

from multiprocessing import Process
from threading import Thread
import time
def piao(name):
    print("%s piaoing" % name)
    time.sleep(2)
    print("%s piao end" % name)
if __name__ =="__main__":
    # p=Process(target=piao,args=("ya",))
    # p.start()
    t = Thread(target=piao, args=("ya",))
    t.start()
    print("The main is end.")

 2、同一进程内的多个线程共享进程地址空间，如子进程和父进程之间内存隔离

from multiprocessing import Process
n=100
def task():
    global n
    n=0
if __name__ =="__main__":
    p = Process(target=task,)
    p.start()
    p.join()
    print("The main.",n)

线程公用进程内存

from threading import Thread
n=100
def task():
    global n
    n=0
if __name__ =="__main__":
    p = Thread(target=task,)
    p.start()
    p.join()
    print("The main.",n)

 

3、看一下pid

主进程和子进程id不一样

import os
from multiprocessing import Process,current_process
def task():
    #print(current_process().pid)#查看当前进程id
    #也可以用os.getpid()方法
    print("子进程pid",os.getpid())
    print("父进程pid", os.getppid())
if __name__ =="__main__":
    p = Process(target=task,)
    p.start()
    print("The main.",current_process().pid)

线程中pid和主进程pid一样，因线程属于主进程

from threading import Thread
import os
def task():
    print("‘子’线程pid",os.getpid())
if __name__ =="__main__":
    p = Thread(target=task,)
    p.start()
    print("The main.",os.getpid())