Python多线程生成器异常：Generator already executing的解决方法

    import threading
    '''
    A generic iterator and generator that takes any iterator and wrap it to make it thread safe.
    This method was introducted by Anand Chitipothu in http://anandology.com/blog/using-iterators-and-generators/
    but was not compatible with python 3. This modified version is now compatible and works both in python 2.8 and 3.0 
    '''
    class threadsafe_iter:
    """Takes an iterator/generator and makes it thread-safe by
    serializing call to the `next` method of given iterator/generator.
    """
    def __init__(self, it):
        self.it = it
        se