python – 线程类中init的相反

发布时间：2020-12-16 23:06:02 所属栏目：Python 来源：网络整理

导读：我知道当你创建像newThread = MyThread(property)这样的类并且newthread.start()触发run()时会自动调用__init __().我正在寻找的是在线程终止之前自动调用的东西,所以我不必在每个return语句之前显式调用self.cleanUp(). class MyThread(Thread): def __init

我知道当你创建像newThread = MyThread(property)这样的类并且newthread.start()触发run()时会自动调用__init __().我正在寻找的是在线程终止之前自动调用的东西,所以我不必在每个return语句之前显式调用self.cleanUp().

class MyThread(Thread): 

    def __init__(self,property): 
        Thread.__init__(self)
        self.property = property

    def cleanUp(self):
        # Clean up here

    def run(self):
        # Do some stuff
        self.cleanUp() # Current work around
        return

解决方法

一种方法是使Thread子类也为 context manager.这将有效地使__exit __()成为您想要触发的特殊方法.

以下显示了我的建议.注意：我重命名了您传递构造函数的属性参数,因为property是Python内置的名称.

from threading import Thread
import time

TEST_THREAD_EXCEPTION = False  # change as desired

class MyThread(Thread):

    def __init__(self,attribute):
        Thread.__init__(self)
        self.attribute = attribute

    def cleanup(self):
        # Clean up here
        print('  cleaning up after thread')

    def run(self):
        if TEST_THREAD_EXCEPTION:
            raise RuntimeError('OOPS!')  # force exception
        print('  other thread now running...')
        time.sleep(2)  # Do something...

    def __enter__(self):
        try:
            self.run()
        except Exception as exc:
            print('Error: {} exception raised by thread'.format(exc))
            raise  # reraise the exception
        return self

    def __exit__(self,*args):
        self.cleanup()

print('main thread begins execution')
with MyThread('hello') as thread:
    print('doing other things in main thread while other thread is running')
print('main thread continuing...')

输出：

main thread begins execution
  other thread now running...
doing other things in main thread while other thread is running
  cleaning up after thread
main thread continuing on...

如果将TEST_THREAD_EXCEPTION更改为True,则不会调用cleanup(),因为线程未成功运行 – 尽管您可以根据需要更改它,但可能还需要确保它不会被调用两次.以下是上述代码在这种情况下的作用：

main thread begins execution
Error: OOPS! exception raised by thread
Traceback (most recent call last):
  File "opposite_init.py",line 37,in <module>
    with MyThread('hello') as thread:
  File "opposite_init.py",line 27,in __enter__
    self.run()
  File "opposite_init.py",line 21,in run
    raise RuntimeError('OOPS!')  # force exception
RuntimeError: OOPS!

（编辑：李大同）

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python – 线程类中__init__的相反

解决方法

python – 线程类中init的相反