“ValueError:需要多于1个值才能解包”使用多处理

Question

我有这个代码：

def characterize_file(filename):
    try:
        # …
        return (filename, characterization)
    except Exception as e:
        print(filename)
        traceback.print_exc()
        raise e

def write_characterization(args):
    # …
    p = multiprocessing.Pool(3)
    characterizations = p.imap(characterize_file, args)
    for (i, (filename, characterization)) in enumerate(characterizations):
        pass # …

有时，我会得到一个异常，没有任何其他输出：

^{pr2}$

它从哪里来？try语句不应该捕捉错误并打印吗？在