How to Force End a Thread in Python?

Question

How to Force End a Thread in Python?

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#1 by (0 votes)

5

How to force Thread completion in Python?

Example:

import threading


def funcao():
    print("Função executando em tarefa paralela.")
    print("Função executando em tarefa paralela.")
    print("Existem outras threads dela mas só essa tem que ser finalizada")
    print("Não vai ficar nenhum laço de repetição aqui checando condição para poder finalizar ela não, a finalização precisa ser forçada de fora")


threading.Thread(target=funcao).start()

I need to force the end of it without using tricks like return, break, raise, daemom, etc. inside the function that expects something to be able to finish it. But something outside this function that forces you to finish

python

asked by anonymous 23.06.2018 / 08:45

1 answer

Passing a variable within a procedure Inform field value TFDAutoIncField using FDQuery

score 0 · Answer 1

You can use asyncio , where corotines / tasks ( Task ) are similar to threads but are not actually threads as defined by the OS, and therefore have no context-switching or external your own program.

Suppose you want to calculate the square of a list of numbers from 0 to 4, but you want to cancel the execution of the calculation of 2 ^ 2 if the result of some other function is 9, without having inside the calculation corotina no check as you asked.

If you do this with asyncio :

import asyncio
import random

# Função que simula algum trabalho de cada tarefa/corotina (semelhante a uma thread)
async def retornar_quadrado(n):
    if n == 2:
        await asyncio.sleep(10)  # A função que será cancelada demora mais.
    else:
        await asyncio.sleep(random.uniform(0.5, 2))  # As outras demoram de 0.5 a 2 segundos.
    return n ** 2


async def main():

    # Criar uma lista de tarefas
    tarefas = []
    for i in range(5):
        tarefa = asyncio.ensure_future(retornar_quadrado(i))
        tarefas.append(tarefa)

    for tarefa_completa in asyncio.as_completed(tarefas):
        try:
            n_quadrado = await tarefa_completa
            print(n_quadrado)
        except asyncio.CancelledError:
            continue

        # Se descobrimos que uma das respostas é 9, cancelamos tarefas[2]
        if n_quadrado == 9 and not tarefas[2].cancelled():
            print('Cancelando tarefas[2]...')
            tarefas[2].cancel()

loop = asyncio.get_event_loop()
loop.run_until_complete(main())

An example result:

16
9
Cancelando tarefas[2]...
0
1

As you can see, once we found 9, we canceled the calculation of 2 ^ 2 and it was never displayed. If you remove the tarefas[2].cancel() line, you will see that the result 4 is displayed, and also that the function will take the 10 seconds that this special case requires.