python 多进程并行编程 ProcessPoolExecutor的实现

yipeiwu_com5年前Python基础

使用 ProcessPoolExecutor

from concurrent.futures import ProcessPoolExecutor, as_completed
import random

斐波那契数列

当 n 大于 30 时抛出异常

def fib(n):
  if n > 30:
    raise Exception('can not > 30, now %s' % n)
  if n <= 2:
    return 1
  return fib(n-1) + fib(n-2)

准备数组

nums = [random.randint(0, 33) for _ in range(0, 10)]
'''
[13, 17, 0, 22, 19, 33, 7, 12, 8, 16]
'''

方案一:submit

submit 输出结果按照子进程执行结束的先后顺序,不可控

 with ProcessPoolExecutor(max_workers=3) as executor:
    futures = {executor.submit(fib, n):n for n in nums}
    for f in as_completed(futures):
      try:
        print('fib(%s) result is %s.' % (futures[f], f.result()))
      except Exception as e:
        print(e)
'''
fib(13) result is 233.
fib(17) result is 1597.
fib(0) result is 1.
fib(22) result is 17711.
fib(19) result is 4181.
can not > 30, now 33
fib(7) result is 13.
fib(12) result is 144.
fib(8) result is 21.
fib(16) result is 987.

'''

等价写法:

 with ProcessPoolExecutor(max_workers=3) as executor:
    futures = {}
    for n in nums:
      job = executor.submit(fib, n)
      futures[job] = n

    for job in as_completed(futures):
      try:
        re = job.result()
        n = futures[job]
        print('fib(%s) result is %s.' % (n, re))
      except Exception as e:
        print(e)
'''
fib(13) result is 233.
fib(17) result is 1597.
fib(0) result is 1.
fib(22) result is 17711.
can not > 30, now 33
fib(7) result is 13.
fib(19) result is 4181.
fib(8) result is 21.
fib(12) result is 144.
fib(16) result is 987.
'''

方案二:map

map 输出结果按照输入数组的顺序

缺点:某一子进程异常会导致整体中断

 with ProcessPoolExecutor(max_workers=3) as executor:
    try:
      results = executor.map(fib, nums)
      for num, result in zip(nums, results):
        print('fib(%s) result is %s.' % (num, result))
    except Exception as e:
      print(e)
'''
fib(13) result is 233.
fib(17) result is 1597.
fib(0) result is 1.
fib(22) result is 17711.
fib(19) result is 4181.
can not > 30, now 33
'''

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持【听图阁-专注于Python设计】。

相关文章

pycharm 使用心得(八)如何调用另一文件中的函数

实现步骤: 1. PyCharm, IDE有个Project setting图标,是给run图标做配置的,配置run file为myfile.py2.复制代码 代码如下:# ------...

解决Python安装时报缺少DLL问题【两种解决方法】

解决Python安装时报缺少DLL问题【两种解决方法】

准备开始学习Python,但是刚准备环境搭建时就遇到了下面的错误: 仔细的看了看,说是缺少DLL。 对于这个问题的解决办法: 方法一: 1. 在安装包上点右键以管理员身份运行 2. C...

Python简单操作sqlite3的方法示例

本文实例讲述了Python简单操作sqlite3的方法。分享给大家供大家参考,具体如下: import sqlite3 def Test1(): #con =sqlite3.co...

python3+PyQt5使用数据库表视图

python3+PyQt5使用数据库表视图

上文提到窗体可以一次性呈现出来自同一记录的各个域,但是对于用户希望能看到多条记录的表来说,就需要使用表格化的视图了。本文通过python3+pyqt5改写实现了python Qt gui...

浅谈pytorch grad_fn以及权重梯度不更新的问题

前提:我训练的是二分类网络,使用语言为pytorch Varibale包含三个属性: data:存储了Tensor,是本体的数据 grad:保存了data的梯度,本事是个Variable...