Python concurrent.futures模块使用实例
这篇文章主要介绍了Python concurrent.futures模块使用实例,文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下
concurrent.futures的作用：
管理并发任务池。concurrent.futures模块提供了使用工作线程或进程池运行任务的接口。线程和进程池API都是一样，所以应用只做最小的修改就可以在线程和进程之间地切换
1、基于线程池使用map()
futures_thread_pool_map.py
#!/usr/bin/env python
# -*- coding: utf-8 -*-
from concurrent import futures
import threading
import time
def task(n):
print('{}: 睡眠 {}'.format(threading.current_thread().name,n))
time.sleep(n / 10)
print('{}: 执行完成 {}'.format(threading.current_thread().name,n))
return n / 10
ex = futures.ThreadPoolExecutor(max_workers=2)
print('main: 开始运行')
results = ex.map(task, range(5, 0, -1)) #返回值是generator 生成器
print('main: 未处理的结果 {}'.format(results))
print('main: 等待真实结果')
real_results = list(results)
print('main: 最终结果: {}'.format(real_results))
运行效果
[root@ mnt]# python3 futures_thread_pool_map.py main: 开始运行 ThreadPoolExecutor-0_0: 睡眠 5 ThreadPoolExecutor-0_1: 睡眠 4 main: 未处理的结果 <generator object Executor.map.<locals>.result_iterator at 0x7f1c97484678> main: 等待真实结果 ThreadPoolExecutor-0_1: 执行完成 4 ThreadPoolExecutor-0_1: 睡眠 3 ThreadPoolExecutor-0_0: 执行完成 5 ThreadPoolExecutor-0_0: 睡眠 2 ThreadPoolExecutor-0_0: 执行完成 2 ThreadPoolExecutor-0_0: 睡眠 1 ThreadPoolExecutor-0_1: 执行完成 3 ThreadPoolExecutor-0_0: 执行完成 1 main: 最终结果: [0.5, 0.4, 0.3, 0.2, 0.1]
2、futures执行单个任务
futures_thread_pool_submit.py
#!/usr/bin/env python
# -*- coding: utf-8 -*-
from concurrent import futures
import threading
import time
def task(n):
print('{}: 睡眠 {}'.format(threading.current_thread().name, n))
time.sleep(n / 10)
print('{}: 执行完成 {}'.format(threading.current_thread().name, n))
return n / 10
ex = futures.ThreadPoolExecutor(max_workers=2)
print('main :开始')
f = ex.submit(task, 5)
print('main: future: {}'.format(f))
print('等待运行结果')
results = f.result()
print('main: result:{}'.format(results))
print('main: future 之后的结果:{}'.format(f))
运行效果
[root@ mnt]# python3 futures_thread_pool_submit.py main :开始 ThreadPoolExecutor-0_0: 睡眠 5 main: future: <Future at 0x7f40c0a6a400 state=running> 等待运行结果 ThreadPoolExecutor-0_0: 执行完成 5 main: result:0.5 main: future 之后的结果:<Future at 0x7f40c0a6a400 state=finished returned float>
3、futures.as_completed()按任意顺序运行结果
futures_as_completed.py
#!/usr/bin/env python
# -*- coding: utf-8 -*-
import random
import time
from concurrent import futures
def task(n):
time.sleep(random.random())
return (n, n / 10)
ex = futures.ThreadPoolExecutor(max_workers=2)
print('main: 开始')
wait_for = [
ex.submit(task, i) for i in range(5, 0, -1)
]
for f in futures.as_completed(wait_for):
print('main: result:{}'.format(f.result()))
运行效果
[root@ mnt]# python3 futures_as_completed.py main: 开始 main: result:(5, 0.5) main: result:(4, 0.4) main: result:(3, 0.3) main: result:(1, 0.1) main: result:(2, 0.2)
4、Future回调之futures.add_done_callback()
futures_future_callback.py
#!/usr/bin/env python
# -*- coding: utf-8 -*-
from concurrent import futures
import time
def task(n):
print('task {} : 睡眠'.format(n))
time.sleep(0.5)
print('task {} : 完成'.format(n))
return n / 10
def done(fn):
if fn.cancelled():
print('done {}:取消'.format(fn.arg))
elif fn.done():
error = fn.exception()
if error:
print('done {} : 错误返回 : {}'.format(fn.arg, error))
else:
result = fn.result()
print('done {} : 正常返回 : {}'.format(fn.arg, result))
if __name__ == '__main__':
ex = futures.ThreadPoolExecutor(max_workers=2)
print('main : 开始')
f = ex.submit(task, 5)
f.arg = 5
f.add_done_callback(done)
result = f.result()
运行效果
[root@ mnt]# python3 futures_future_callback.py main : 开始 task 5 : 睡眠 task 5 : 完成 done 5 : 正常返回 : 0.5
5、Future任务取消之futures.cancel()
futures_future_callback_cancel.py
#!/usr/bin/env python
# -*- coding: utf-8 -*-
from concurrent import futures
import time
def task(n):
print('task {} : 睡眠'.format(n))
time.sleep(0.5)
print('task {} : 完成'.format(n))
return n / 10
def done(fn):
if fn.cancelled():
print('done {}:取消'.format(fn.arg))
elif fn.done():
error = fn.exception()
if error:
print('done {} : 错误返回 : {}'.format(fn.arg, error))
else:
result = fn.result()
print('done {} : 正常返回 : {}'.format(fn.arg, result))
if __name__ == '__main__':
ex = futures.ThreadPoolExecutor(max_workers=2)
print('main : 开始')
tasks = []
for i in range(10, 0, -1):
print('main: submitting {}'.format(i))
f = ex.submit(task, i)
f.arg = i
f.add_done_callback(done)
tasks.append((i, f))
for i, task_obj in reversed(tasks):
if not task_obj.cancel():
print('main: 不能取消{}'.format(i))
ex.shutdown()
运行效果
[root@mnt]# python3 futures_future_callback_cancel.py main : 开始 main: submitting 10 task 10 : 睡眠 main: submitting 9 task 9 : 睡眠 main: submitting 8 main: submitting 7 main: submitting 6 main: submitting 5 main: submitting 4 main: submitting 3 main: submitting 2 main: submitting 1 done 1:取消 done 2:取消 done 3:取消 done 4:取消 done 5:取消 done 6:取消 done 7:取消 done 8:取消 main: 不能取消9 main: 不能取消10 task 10 : 完成 done 10 : 正常返回 : 1.0 task 9 : 完成 done 9 : 正常返回 : 0.9
6、Future异常的处理
futures_future_exception
#!/usr/bin/env python
# -*- coding: utf-8 -*-
from concurrent import futures
def task(n):
print('{} : 开始'.format(n))
raise ValueError('这个值不太好 {}'.format(n))
ex = futures.ThreadPoolExecutor(max_workers=2)
print('main: 开始...')
f = ex.submit(task, 5)
error = f.exception()
print('main: error:{}'.format(error))
try:
result = f.result()
except ValueError as e:
print('访问结果值的异常 {}'.format(e))
运行效果
[root@mnt]# python3 futures_future_exception.py main: 开始... 5 : 开始 main: error:这个值不太好 5 访问结果值的异常 这个值不太好 5
7、Future上下文管理即利用with打开futures.ThreadPoolExecutor()
futures_context_manager.py
#!/usr/bin/env python
# -*- coding: utf-8 -*-
from concurrent import futures
def task(n):
print(n)
with futures.ThreadPoolExecutor(max_workers=2) as ex:
print('main: 开始')
ex.submit(task, 1)
ex.submit(task, 2)
ex.submit(task, 3)
ex.submit(task, 4)
print('main: 结束')
运行效果
[root@ mnt]# python3 futures_context_manager.py main: 开始 2 4 main: 结束
8、基于进程池使用map()
futures_process_pool_map.py
#!/usr/bin/env python
# -*- coding: utf-8 -*-
from concurrent import futures
import os
def task(n):
return (n, os.getpid())
if __name__ == '__main__':
ex = futures.ProcessPoolExecutor(max_workers=2)
results = ex.map(task, range(50, 0, -1))
for n, pid in results:
print('task {} in 进程id {}'.format(n, pid))
运行效果
[root@ mnt]# python3 futures_process_pool_map.py task 5 in 进程id 9192 task 4 in 进程id 8668 task 3 in 进程id 9192 task 2 in 进程id 8668 task 1 in 进程id 9192
9、基于进程池异常处理
futures_process_pool_broken.py
#!/usr/bin/env python
# -*- coding: utf-8 -*-
from concurrent import futures
import os
import signal
def task(n):
return (n, os.getpid())
if __name__ == '__main__':
with futures.ProcessPoolExecutor(max_workers=2) as ex:
print('获取工作进程的id')
f1 = ex.submit(os.getpid)
pid1 = f1.result()
print('结束进程 {}'.format(pid1))
os.kill(pid1, signal.SIGHUP)
print('提交其它进程')
f2 = ex.submit(os.getpid)
try:
pid2 = f2.result()
except futures.process.BrokenProcessPool as e:
print('不能开始新的任务:{}'.format(e))
运行效果
[root@ mnt]# python3 futures_process_pool_broken.py 获取工作进程的id 结束进程 104623 提交其它进程 不能开始新的任务:A process in the process pool was terminated abruptly while the future was running or pending.
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