python 进程和线程(2)

这篇博客是按照博客《进程和线程(1)》中内容用futures改写  with futures.ProcessPoolExecutor() as executor:可以两篇博客对照看。

2改写

from multiprocessing import Pool
from time import sleep
from concurrent import futures
def f(x):
    return x*x
def speak(word):
    for i in range(3):
        print('i am speak:',word,i)
if __name__=='__main__':
    x=[1,2,3]
    speak(x)
    with futures.ProcessPoolExecutor() as executor:
        print(list(executor.map(f,x)))
        print(type(executor.map(f,x)))
# i am speak: [1, 2, 3] 0
# i am speak: [1, 2, 3] 1
# i am speak: [1, 2, 3] 2
# [1, 4, 9]
# <class 'generator'>

2.1.2改写

from multiprocessing import Pool,Process
import time
from concurrent import futures
def f(x):
    time.sleep(2)
    print(x*x)
    return x*x
def speak(word):
    for i in range(3):
        print('i am speak:',word,i)
        time.sleep(2)
if __name__=='__main__':
    startTime=time.time()
    x=[1,2,3]
    # for i in x:
    #     p=Process(target=f,args=(i,))
    #     p.start()
    #     endTimeSub=time.time()
    #     print('usetimesub',endTimeSub-startTime)
    with futures.ProcessPoolExecutor() as executor:
        executor.map(f,x)
        endTimeSub=time.time()
        print('usetimesub',endTimeSub-startTime)
    endTimeMain=time.time()
    print('useTime',endTimeMain-startTime)
# usetimesub 0.1450958251953125
# 1
# 4
# 9
# useTime 2.2364883422851562

在上面改写基础上，如果在子进程中停顿3s，看看结果怎么样？

from multiprocessing import Pool,Process
import time
from concurrent import futures
def f(x):
    time.sleep(2)
    print(x*x)
    return x*x
def speak(word):
    for i in range(3):
        print('i am speak:',word,i)
        time.sleep(2)
if __name__=='__main__':
    startTime=time.time()
    x=[1,2,3]
    # for i in x:
    #     p=Process(target=f,args=(i,))
    #     p.start()
    #     endTimeSub=time.time()
    #     print('usetimesub',endTimeSub-startTime)
    with futures.ProcessPoolExecutor() as executor:
        executor.map(f,x)
        endTimeSub=time.time()
        time.sleep(3)
        print('usetimesub',endTimeSub-startTime)
    endTimeMain=time.time()
    print('useTime',endTimeMain-startTime)
# 1
# 4
# 9
# usetimesub 0.1621077060699463
# useTime 3.2041215896606445

可见：1、总使用只时间增加了1s左右；2、主程序没有继续往下走，先等子进程全部执行完再往下走，useTime都是在最后，直接使用p=Process(target=f,args=(i,))，则是新开一个子进程，主进程继续往下走，注意两者区别；3、比较两者执行时间