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python 多进程并行编程 ProcessPoolExecutor的实现

更新时间:2020-08-03 00:24:01 作者:startmvc
使用ProcessPoolExecutorfromconcurrent.futuresimportProcessPoolExecutor,as_completedimportrandom斐波那契数列当n

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
'''

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python ProcessPoolExecutor python 多进程并行