python - pool.map_async 的打印进度

Question

我有以下功能

from multiprocessing import Pool
def do_comparison(tupl):
    x, y = tupl # unpack arguments
    return compare_clusters(x, y)

def distance_matrix(clusters, condensed=False):
    pool = Pool()
    values = pool.map_async(do_comparison, itertools.combinations(clusters, 2)).get()
    do stuff

是否可以打印pool.map_async(do_comparison, itertools.combinations(clusters, 2)).get()的进度？我通过像这样向 do_comparison 添加计数来尝试

count = 0
def do_comparison(tupl):
    global count
    count += 1
    if count % 1000 == 0:
        print count
    x, y = tupl # unpack arguments
    return compare_clusters(x, y)

但除了它看起来不是一个好的解决方案之外，数字直到脚本结束才会打印。有什么好的方法吗？

Answer 1

我按如下方式跟踪进度:

import multiprocessing
import time

class PoolProgress:
  def __init__(self,pool,update_interval=3):
    self.pool            = pool
    self.update_interval = update_interval
  def track(self, job):
    task = self.pool._cache[job._job]
    while task._number_left>0:
      print("Tasks remaining = {0}".format(task._number_left*task._chunksize))
      time.sleep(self.update_interval)


def hi(x): #This must be defined before `p` if we are to use in the interpreter
  time.sleep(x//2)
  return x

a = list(range(50))

p   = multiprocessing.Pool()
pp  = PoolProgress(p)

res = p.map_async(hi,a)

pp.track(res)