多进程

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多进程

多进程 Multiprocessing 和多线程 threading 类似，用来弥补 threading 的一些劣势（例如GIL）， Python 出了一个 multiprocessing

多进程与多线程

使用方法几乎一致

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import multiprocessing
import threading

def job_t(a,d):
    print('tttt')

def job_p(a,d):
    print('pppp')


t1 = threading.Thread(target=job_t,args=(1,2))
p1 = multiprocessing.Process(target=job_p,args=(1,2))
t1.start()
p1.start()

t1.join()
p1.join()

进程结果 Queue()

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import multiprocessing as mp

def job(q):
    res=0
    for i in range(1000):
        res+=i+i**2+i**3
    q.put(res)    #queue

if __name__=='__main__':
    q = mp.Queue()
    p1 = mp.Process(target=job,args=(q,))
    p2 = mp.Process(target=job,args=(q,))
    p1.start()
    p2.start()
    p1.join()
    p2.join()
    res1 = q.get()
    print(res1)
    res2 = q.get()
    print(res2)
    print(res1+res2)

效率对比

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import time
import multiprocessing 
import threading

def _cost_time(func):
    def warpper(*args,**kw):
        start_time = time.time()
        func(*args,**kw)
        end_time = time.time()
        print('cost time :',end_time - start_time)
    return warpper
    

def job(q):
    res = 0
    for i in range(1000000):
        res += i + i**2 + i**3
    q.put(res) # queue

@_cost_time
def normal():
    res = 0
    for _ in range(2):
        for i in range(1000000):
            res += i + i**2 + i**3
    print('normal:', res)
    

@_cost_time
def multithread():
    q = multiprocessing.Queue() 
    t1 = threading.Thread(target=job, args=(q,))
    t2 = threading.Thread(target=job, args=(q,))
    t1.start()
    t2.start()
    t1.join()
    t2.join()
    res1 = q.get()
    res2 = q.get()
    print('multithread:', res1 + res2)


@_cost_time
def multicore():
    q =  multiprocessing.Queue()
    p1 = multiprocessing .Process(target=job, args=(q,))
    p2 =  multiprocessing .Process(target=job, args=(q,))
    p1.start()
    p2.start()
    p1.join()
    p2.join()
    res1 = q.get()
    res2 = q.get()
    print('multicore:',res1 + res2)


normal()
multithread()
multicore()

打印结果

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('normal:', 499999666667166666000000L)
('cost time :', 0.8630490303039551)
('multithread:', 499999666667166666000000L)
('cost time :', 1.8854999542236328)
('multicore:', 499999666667166666000000L)
('cost time :', 0.47038793563842773)

耗时 多进程 < 普通 < 多线程 。

多线程不适合计算密集型