同异步调用、shutdown参数

1.使用shutdown

ex.shutdown(wait=True)是进程池内部的进程都执行完毕，才会关闭，然后执行后续代码 
如果改成false呢？看如下代码

from concurrent.futures import ProcessPoolExecutor
import  time
def task(name):
    print("name",name)
    time.sleep(1)

if __name__ == "__main__":
    start = time.time()
    ex = ProcessPoolExecutor(2)

    for i in range(5):
        ex.submit(task,"safly%d"%i)
    ex.shutdown(wait=False)

    print("main")
    end = time.time()
    print(end - start)

输出如下：

main
0.01500844955444336
name safly0
name safly1
name safly2
name safly3
name safly4

使用submit同步调用

同步调用：提交/调用一个任务，然后就在原地等着，等到该任务执行完毕拿到结果，再执行下一行代码

from concurrent.futures import ProcessPoolExecutor
import time, random, os

def piao(name, n):
    print('%s is piaoing %s' % (name, os.getpid()))
    time.sleep(1)
    return n ** 2


if __name__ == '__main__':
    p = ProcessPoolExecutor(2)
    start = time.time()
    for i in range(5):
        res=p.submit(piao,'safly %s' %i,i).result() #同步调用
        print(res)

    p.shutdown(wait=True)
    print('主', os.getpid())

    stop = time.time()

输出如下：

E:pythonpython_sdkpython.exe "E:/python/py_pro/4 进程池.py"
safly 0 is piaoing 12996
0
safly 1 is piaoing 14044
1
safly 2 is piaoing 12996
4
safly 3 is piaoing 14044
9
safly 4 is piaoing 12996
16
主 12932
5.202786684036255

Process finished with exit code 0

使用submit异步调用

异步调用: 提交/调用一个任务，不在原地等着，直接执行下一行代码

# from multiprocessing import Process,Pool
from concurrent.futures import ProcessPoolExecutor
import time, random, os

def piao(name, n):
    print('%s is piaoing %s' % (name, os.getpid()))
    time.sleep(1)
    return n ** 2


if __name__ == '__main__':
    p = ProcessPoolExecutor(2)
    objs = []
    start = time.time()
    for i in range(5):
        obj = p.submit(piao, 'safly %s' % i, i)  # 异步调用
        objs.append(obj)

    p.shutdown(wait=True)
    print('主', os.getpid())
    for obj in objs:
        print(obj.result())

    stop = time.time()
    print(stop - start)

输出结果：

E:pythonpython_sdkpython.exe "E:/python/py_pro/4 进程池.py"
safly 0 is piaoing 1548
safly 1 is piaoing 7872

safly 2 is piaoing 1548
safly 3 is piaoing 7872


safly 4 is piaoing 1548


主 7808
0
1
4
9
16
3.202626943588257