what is python dangling circular ref?-灵析社区

下面是wsgi web server的片段demo def start_response(status, response_headers, exc_info=None): if exc_info: try: if headers_sent: # Re-raise original exception if headers sent raise exc_info[1].with_traceback(exc_info[2]) finally: exc_info = None # avoid dangling circular ref elif headers_set: raise AssertionError("Headers already set!") headers_set[:] = [status, response_headers] # Note: error checking on the headers should happen here, # *after* the headers are set. That way, if an error # occurs, start_response can only be re-called with # exc_info set. return write 我想问: `exc_info = None # avoid dangling circular ref` 这里有什么必要这样操作？ 这和迷途指针有什么关系吗？