python Pool常用函數用法總結

#coding: utf-8
import multiprocessing
import time
 
 
def func(msg):
    print("msg:", msg)
    time.sleep(3)
    print("end")
 
 
if __name__ == "__main__":
    cores = multiprocessing.cpu_count()
    pool = multiprocessing.Pool(processes=cores)
    print("Adding tasks...")
    for i in range(cores):
        msg = "hello %d" %(i)
        pool.apply_async(func, (msg, ))   #維持執行的進程總數為processes，當一個進程執行完畢後會添加新的進程進去
    print("Starting tasks...")
    pool.close()
    pool.join()   #調用join之前，先調用close函數，否則會出錯。執行完close後不會有新的進程加入到pool,join函數等待所有子進程結束
    print("Sub-process(es) done.")

# -*- coding:utf-8 -*-
from multiprocessing import Pool
import os, time, random
def worker(msg):
  t_start = time.time()
  print("%s開始執行,進程號為%d" % (msg,os.getpid()))
  # random.random()隨機生成0~1之間的浮點數
  time.sleep(random.random()*2) 
  t_stop = time.time()
  print(msg,"執行完畢，耗時%0.2f" % (t_stop-t_start))
po = Pool(3) # 定義一個進程池，最大進程數3
for i in range(0,10):
  # Pool().apply_async(要調用的目標,(傳遞給目標的參數元祖,))
  # 每次循環將會用空閑出來的子進程去調用目標
  po.apply_async(worker,(i,))
print("----start----")
po.close() # 關閉進程池，關閉後po不再接收新的請求
po.join() # 等待po中所有子進程執行完成，必須放在close語句之後
print("-----end-----")