使python生成器在后台运行 [英] Make python generator run in background

问题描述

现在我有一些代码可以大致执行以下操作

Right now I have some code that does roughly the following

def generator():

    while True:
        value = do_some_lengthy_IO()
        yield value 

def model():

    for datapoint in generator():
        do_some_lengthy_computation(datapoint)

现在，I/O和计算是串行进行的.理想情况下，应该并行运行 (生成器已准备好下一个值)，因为它们只共享要传递的值，而没有其他共享.我开始研究这个问题，并对multiprocessing，threading和async东西感到非常困惑，无法获得一个最小的工作示例.另外，由于其中一些功能似乎是最新功能，因此我正在使用Python 3.6.

Right now, the I/O and the computation happen in serial. Ideally the should be running in parallel concurrently (the generator having ready the next value) since they share nothing but the value being passed. I started looking into this and got very confused with the multiprocessing, threading, and async stuff and could not get a minimal working example going. Also, since some of this seems to be recent features, I am using Python 3.6.

推荐答案

我最终弄清楚了它.最简单的方法是使用multiprocessing包，并使用管道与子进程进行通信.我写了一个可以使用任何生成器的包装器

I ended up figuring it out. The simplest way is to use the multiprocessing package and use a pipe to communicate with the child process. I wrote a wrapper that can take any generator

import time
import multiprocessing

def bg(gen):
    def _bg_gen(gen, conn):
        while conn.recv():
            try:
                conn.send(next(gen))
            except StopIteration:
                conn.send(StopIteration)
                return

    parent_conn, child_conn = multiprocessing.Pipe()
    p = multiprocessing.Process(target=_bg_gen, args=(gen, child_conn))
    p.start()

    parent_conn.send(True)
    while True:
        parent_conn.send(True)
        x = parent_conn.recv()
        if x is StopIteration:
            return
        else:
            yield x

def generator(n):
    for i in range(n):
        time.sleep(1)
        yield i

#This takes 2s/iteration
for i in generator(100):
    time.sleep(1)

#This takes 1s/iteration
for i in bg(generator(100)):
    time.sleep(1)

目前唯一缺少的是，对于无限生成器，该过程永远不会终止，但是可以通过执行parent_conn.send(False)轻松添加.

The only missing thing right now is that for infinite generators the process is never killed but that can be easily added by doing a parent_conn.send(False).

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