Python asynchronous programming demo: process/thread pool

using multiprocessing

from multiprocessing import Pool

def a(num):
    print num

if __name__ == "__main__":
    pool = Pool(3)
    for i in range(10):
        pool.apply_async(a,args=(i,))
    pool.close()
    pool.join()

using concurrent

import concurrent
from concurrent import futures
with concurrent.futures.ThreadPoolExecutor(max_workers=5) as executor:
    for item in number_list:
        executor.submit(evaluate_item,  item)

or

import concurrent
from concurrent import futures
with concurrent.futures.ProcessPoolExecutor(max_workers=5) as executor:
    for item in number_list:
        executor.submit(evaluate_item,  item)

Just like ThreadPoolExecutor, ProcessPoolExecutor is an executor that uses a thread pool to execute tasks in parallel. However, unlike ThreadPoolExecutor, ProcessPoolExecutor uses a multi-core processing module that allows us to not be limited by the GIL and greatly reduces execution time.

using asyncio

import asyncio
import datetime
import time

def function_1(end_time, loop):
    print ("function_1 called")
    if (loop.time() + 1.0) < end_time:
        loop.call_later(1, function_2, end_time, loop)
    else:
        loop.stop()

def function_2(end_time, loop):
    print ("function_2 called ")
    if (loop.time() + 1.0) < end_time:
        loop.call_later(1, function_3, end_time, loop)
    else:
        loop.stop()

def function_3(end_time, loop):
    print ("function_3 called")
    if (loop.time() + 1.0) < end_time:
        loop.call_later(1, function_1, end_time, loop)
    else:
        loop.stop()

def function_4(end_time, loop):
    print ("function_4 called")
    if (loop.time() + 1.0) < end_time:
        loop.call_later(1, function_4, end_time, loop)
    else:
        loop.stop()

loop = asyncio.get_event_loop()

end_loop = loop.time() + 9.0
loop.call_soon(function_1, end_loop, loop)
# loop.call_soon(function_4, end_loop, loop)
loop.run_forever()
loop.close()

Reference

• https://python-parallel-programmning-cookbook.readthedocs.io/zh_CN/latest/chapter4/02_Using_the_concurrent.futures_Python_modules.html

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