线程vs进程

线程vs进程

速度

from multiprocessing import  Process
from threading import Thread
import time

def test():
    pass


if __name__ == '__main__':
    p = Process(target=test)
    t = Thread(target=test)
    start1 = time.time()
    p.start()
    p.join()
    end1 = time.time()
    start2 = time.time()
    t.start()
    t.join()
    end2 = time.time()

    print(end1 - start1)
    print(end2 - start2)

线程要远快于进程

资源共享

from multiprocessing import  Process
from threading import Thread
import time
x = 1
def test():
    global x
    x= 100
    print("我完成了")


if __name__ == '__main__':
    # 查看进程是否可修改数据

    p = Process(target=test)
    p.start()
    time.sleep(2)
    print(x)


    # 查看线程是否可修改数据

    # t = Thread(target=test)
    # t.start()
    #
    # time.sleep(1)
    # print(x)

线程共享资源

进程间彼此隔离

何时使用多进程 和 何时使用多进程

import time
from multiprocessing import Process
from threading import Thread,Timer


# 计算密集型函数
def compute_intensive():
    res = 0
    for i in range(10000000):
        res += 1


def block_intensive():
    time.sleep(3)


if __name__ == '__main__':
    start = time.time()
    p_l = []
    for i in range(10):
        p = Process(target=compute_intensive)
        p_l.append(p)
        p.start()
    for i in p_l:
        i.join()
    end = time.time()
    print("多进程计算密集型用时", end - start, '秒')


    start1 = time.time()
    t_l = []
    for i in range(10):
        t = Thread(target=compute_intensive)
        t_l.append(t)
        t.start()
    for i in t_l:
        i.join()
    end1 = time.time()
    print("多线程计算密集型用时", end1 - start1, '秒')


    print()


    start2 = time.time()
    p_l = []
    for i in range(10):
        p = Process(target=block_intensive)
        p_l.append(p)
        p.start()
    for i in p_l:
        i.join()
    end2 = time.time()
    print("多进程IO密集型用时", end2 - start2, '秒')


    start3 = time.time()
    t_l = []
    for i in range(10):
        t = Thread(target=block_intensive)
        t_l.append(t)
        t.start()
    for i in t_l:
        i.join()
    end3 = time.time()
    print("多线程IO密集型用时", end3 - start3, '秒')

计算密集型使用多进程

IO密集型使用多线程