Python的threading和multiprocessing

Python的threading

基础用法, 通过 threading.Thread() 创建线程, 然后 start() 和 join()

import time

import threading

def do_something(seconds):

	print('Sleeping...')

	time.sleep(seconds)

	print('Done')

start = time.perf_counter()

threads = []

for _ in range(10):

	t = threading.Thread(target = do_something, args=[1])

	t.start()

	threads.append(t)

for t in threads:

	t.join()

finish = time.perf_counter()

print('Total: {}'.format(round(finish - start, 2)))

使用线程池. 使用as_completed, 可以阻塞并按完成顺序输出结果, 而直接用executor.map()会将结果收集完成后一起返回.

import time

import threading

from concurrent import futures

def do_something(seconds):

	print('Sleeping...')

	time.sleep(seconds)

	return 'Done ' + str(seconds)

start = time.perf_counter()

with futures.ThreadPoolExecutor(max_workers=3) as executor:

	secs = [3, 2.5, 2, 2.2, 0.5]

	results = [executor.submit(do_something, sec) for sec in secs]

	for f in futures.as_completed(results):

		print(f.result())

# 注意区别

with futures.ThreadPoolExecutor() as executor:

	secs = [3, 2.5, 2, 2.2, 0.5]

	# 下面这行实际是阻塞的

	results = executor.map(do_something, secs)

	for result in results:

		print(result)

finish = time.perf_counter()

print('Total: {}'.format(round(finish - start, 2)))

.

Python的multiprocessing

.在使用multiprocessing时, 子进程里的print()是会滞后打印的.

import time

import multiprocessing

import logging

def do_something(seconds):

	print('Sleeping...', seconds)

	time.sleep(seconds)

	return 'Done ' + str(seconds)

if __name__ == '__main__':

	multiprocessing.log_to_stderr()

	logger = multiprocessing.get_logger()

	logger.setLevel(logging.INFO)

	start = time.perf_counter()

	secs = [3.1, 3.5, 3.1, 3.2, 3.5, 3.3]

	processes = []

	for sec in secs:

		p = multiprocessing.Process(target=do_something, args=(sec,))

		p.start()

		processes.append(p)

	for p in processes:

		p.join()

	finish = time.perf_counter()

	print('Total: {}'.format(round(finish - start, 2)))

	print()

	pool = multiprocessing.Pool(processes=3)

	print(pool.map(do_something, secs))

	finish = time.perf_counter()

	print('Total: {}'.format(round(finish - start, 2)))

.