Table of Contents
Requirements
Key points
Implementation
Exception definition and special value (0) definition
func function definition
callback definition
Thread pool processing
The main function starts a test process
Result verification
Home Backend Development Python Tutorial Detailed explanation of Threadpool thread pool task termination sample code in python

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

Mar 20, 2017 pm 01:09 PM

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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