Detailed explanation of Threadpool thread pool task termination sample code in python

高洛峰

Release： 2017-03-20 13:09:56

Original

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Requirements

Join us and we need to process a series of single digits (0~9). If it is an odd number, we need to loop to print it; if it is an even number, wait for the corresponding time and complete all tasks; if it is 0 It is an error, but there is no need to terminate the task and some processing can be customized.

Key points

Define funcFunctionProcessing requirements

Callback processing returns results, only even numbers and 0 are returned; odd numbers will always be executed; thread control is required Pool status , you need to throw an exception for even numbers and 0, and capture exception handling .

threadpool defines thread pool concurrency

Implementation

# -*- coding: utf-8 -*-
from threadpool import makeRequests, ThreadPool
import time
from multiprocessing import Process

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Exception definition and special value (0) definition

class Finish(SyntaxWarning):
    pass

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class PauseInfo(SyntaxWarning):
    pass
pause_num = 0

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func function definition

Returns False when 0, returns True for other even numbers

def func(para):
    if para == pause_num:
        print('start for %d and wait %ds' % (para, 4))
        time.sleep(4)
        print('error bcs ',para)
        return False
    if para % 2 == 0:
        print('start for %d and wait %ds' % (para, para))
        time.sleep(para)
        print('stop for', para)
        return True
    while True:
        print('continue for', para)
        time.sleep(para)

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callback definition

def callback(request, result):
    if result:
        raise Finish
    else:
        raise PauseInfo

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Thread pool processing

Finish marks the completion of the task, and induces an exception again to exit the thread pool processing;

def main_thread(paras):
    pool = ThreadPool(10)
    requests = makeRequests(callable_=func, args_list=paras, callback=callback)
    [pool.putRequest(req) for req in requests]
    while True:
        try:
            pool.wait()
        except Finish as e:
            raise SystemExit
        except PauseInfo as e:
            print('Pause bcs %d but will continue' % pause_num)
        except Exception as e:
            print('Unknown error so will quit')
            raise SystemExit

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The main function starts a test process

if name == 'main':
    while True:
        s = input('Input number list to test and any other word to quit\n')
        paras = []
        for para in s:
            if para.isnumeric():
                paras.append(int(para))
            else:
                break
        try:
            thread_test = Process(target=main_thread, args=(paras,))
            thread_test.start()
            thread_test.join(timeout=20)
        except TimeoutError as e:
            print('task timeout')
        except Exception as e:
            print('unknow error:',e)

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Result verification

Processing 108, you can see from the print that 1 is processed in a loop, and an error is reported when 0 is processed; 8 is processed and the task End

Input number list to test and any other word to quit
108
continue for 1
start for 0 and wait 4s
start for 8 and wait 8s
continue for 1
continue for 1
continue for 1
error bcs 0
continue for 1
Pause bcs 0 but will continue
continue for 1
continue for 1
continue for 1
continue for 1
stop for 8
Input number list to test and any other word to quit

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