Python concurrent.futures模块使用实例
作者:小粉优化大师
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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