如何从python中的线程获取返回值？

  • Z时代
  • 2024-01-10
  • 分类：问答

foo下面的函数返回一个字符串'foo'。我如何获取'foo'从线程目标返回的值？

from threading import Thread
def foo(bar):
    print('hello {}'.format(bar))
    return 'foo'
thread = Thread(target=foo, args=('world!',))
thread.start()
return_value = thread.join()

上面显示的“一种显而易见的方法”不起作用：thread.join()return None。

回答：

我见过的一种方法是将可变对象（例如列表或字典）与索引或某种其他标识符一起传递给线程的构造函数。然后，线程可以将其结果存储在该对象的专用插槽中。例如：

def foo(bar, result, index):
    print 'hello {0}'.format(bar)
    result[index] = "foo"
from threading import Thread
threads = [None] * 10
results = [None] * 10
for i in range(len(threads)):
    threads[i] = Thread(target=foo, args=('world!', results, i))
    threads[i].start()
# do some other stuff
for i in range(len(threads)):
    threads[i].join()
print " ".join(results)  # what sound does a metasyntactic locomotive make?

如果你确实想join()返回被调用函数的返回值，则可以使用如下所示的Thread子类来实现：

from threading import Thread
def foo(bar):
    print 'hello {0}'.format(bar)
    return "foo"
class ThreadWithReturnValue(Thread):
    def __init__(self, group=None, target=None, name=None,
                 args=(), kwargs={}, Verbose=None):
        Thread.__init__(self, group, target, name, args, kwargs, Verbose)
        self._return = None
    def run(self):
        if self._Thread__target is not None:
            self._return = self._Thread__target(*self._Thread__args,
                                                **self._Thread__kwargs)
    def join(self):
        Thread.join(self)
        return self._return
twrv = ThreadWithReturnValue(target=foo, args=('world!',))
twrv.start()
print twrv.join()   # prints foo

由于名称修改，这有点麻烦，并且它访问特定于Thread实现的“私有”数据结构…但是它可以工作。

对于python3

class ThreadWithReturnValue(Thread):
    def __init__(self, group=None, target=None, name=None,
                 args=(), kwargs={}, Verbose=None):
        Thread.__init__(self, group, target, name, args, kwargs)
        self._return = None
    def run(self):
        print(type(self._target))
        if self._target is not None:
            self._return = self._target(*self._args,
                                                **self._kwargs)
    def join(self, *args):
        Thread.join(self, *args)
        return self._return

以上是 如何从python中的线程获取返回值？ 的全部内容， 来源链接： utcz.com/qa/435187.html

回到顶部