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私はこの方法でセマフォを介してスレッドの数を追跡しています:

#!/usr/bin/python3
import threading

class MyThread(threading.Thread):

    max_threads           = 5
    max_threads_semaphore = threading.BoundedSemaphore(value=max_threads)
    semaphore_timeout     = 60 

    def __init__(self, target=None, name=None, args=(), kwargs={}):
        super().__init__(target=target, name=name, args=args, kwargs=kwargs)

    def start(self):
        semaphore_aquired = self.max_threads_semaphore.acquire(blocking=True, timeout=self.semaphore_timeout)
        if semaphore_aquired:
            print("Sempahore acquired by:", self.name)
            super().start()
        else:
            raise OSError("Time out aquiring max threads semaphore to start new thread")

    def join(self):
        super().join()
        semaphore_released = self.max_threads_semaphore.release()

これは機能しますが、私が望む方法ではありません。できるようになりたい：

def print_test(num):
    print("executing:", num)
    sleep(10)
    print("end of execution:", num)

threads_dict = dict()
thread_range = range(1,20)
for i in thread_range:
    threads_dict[i] = MyThread(target=print_test(i))
    threads_dict[i].start()
for i in thread_range:
    threads_dict[i].join()
    print("joined:", threads_dict[i].name)

明らかに、5 つのスレッドが開始されると ( max_threads)、スクリプトはセマフォのタイムアウトに達するまでデッドロック状態になります。

メソッドは新しいスレッドでstart()メソッドを起動すると思いました。マニュアルrun()から：

start() スレッド オブジェクトごとに最大 1 回呼び出す必要があります。オブジェクトの run() メソッドが別の制御スレッドで呼び出されるように調整します。

だからMyThread私はその部分を次のように置き換えましたjoin()：

def run(self):
    super().run()
    semaphore_released = self.max_threads_semaphore.release()
    print("Sempahore released by:", self.name)

ただし、このコードは新しいスレッドでは実行されません。出力は次のとおりです。

executing: 1
end of execution: 1
Sempahore acquired by: Thread-1
Sempahore released by: Thread-1
executing: 2
end of execution: 2
Sempahore acquired by: Thread-2
Sempahore released by: Thread-2
executing: 3
end of execution: 3
Sempahore acquired by: Thread-3
Sempahore released by: Thread-3
executing: 4
end of execution: 4
Sempahore acquired by: Thread-4
Sempahore released by: Thread-4
executing: 5
end of execution: 5
Sempahore acquired by: Thread-5
Sempahore released by: Thread-5
executing: 6
end of execution: 6
Sempahore acquired by: Thread-6
executing: 7
Sempahore released by: Thread-6
end of execution: 7
Sempahore acquired by: Thread-7
executing: 8
Sempahore released by: Thread-7
end of execution: 8
Sempahore acquired by: Thread-8
executing: 9
Sempahore released by: Thread-8
end of execution: 9
Sempahore acquired by: Thread-9
joined: Thread-1
joined: Thread-2
joined: Thread-3
joined: Thread-4
joined: Thread-5
joined: Thread-6
joined: Thread-7
joined: Thread-8
Sempahore released by: Thread-9
joined: Thread-9

threading.Threadターゲット関数が終了したときにセマフォを自動的に解放するために、関数をオーバーロードする方法はありますか?

出力がそうでない理由がわかりません：

Sempahore acquired by: Thread-1
executing: 1
Sempahore acquired by: Thread-2
executing: 2
Sempahore acquired by: Thread-3
executing: 3
Sempahore acquired by: Thread-4
executing: 4
Sempahore acquired by: Thread-5
executing: 5
(sleep 10 secondes)
end of execution: 1
Sempahore released by: Thread-1
Sempahore acquired by: Thread-6
executing: 6
etc..
4

1 に答える 1

1

「変な」出力についての質問は。これは、新しいスレッドを作成する前にメイン スレッドでprint_test(i)を呼び出すためです。

threads_dict[i] = MyThread(target=print_test(i))

これはprint_test(i)関数の実行です。そして結果としてprint_test(i)関数実行の結果を対象に貼り付けます。

これを修正してみてください：

threads_dict[i] = MyThread(target=print_test, args=[i,])

この修正後、次のような出力が得られました。

('Sempahore acquired by:', 'Thread-1')
('Sempahore acquired by:', 'Thread-2')
('executing:', 1)
('Sempahore acquired by:', 'Thread-3')
('executing:', 2)
('Sempahore acquired by:', 'Thread-4')
('executing:', 3)
('Sempahore acquired by:', 'Thread-5')
('executing:', 4)
('executing:', 5)
('end of execution:', 1)
('Sempahore released by:', 'Thread-1')
('Sempahore acquired by:', 'Thread-6')
...
于 2013-08-30T10:57:24.087 に答える