与线程类中的__init__相反

Question

我知道当你创建一个类newThread = MyThread(property)并且run()被触发时会自动调用__init __()newthread.start().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self.cleanUp()在每个return语句之前显式调用.

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

Answer 1

一种方法是通过使Thread子类也成为上下文管理器.这将有效地使__exit__()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property您传递构造函数的参数,因为它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...

如果更改TEST_THREAD_EXCEPTION为True,cleanup() 则不会被调用,因为线程未成功运行 - 尽管如果您愿意可以更改它,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!