python - Tornado .gen.BadYieldError : yielded unknown object None

Question

我正在使用 Python 和 Tornado 构建带有 jquery UI slider 元素的基本应用程序。我的目标是，当用户与 slider 交互时，它将向 python 函数发送一个值，结果将显示在 python 控制台中。我的 custom.js 是:

$(function() {
$("#slider-range-max").slider({
    min : 0,
    max : 100,
    slide : function(event, ui) {
        $("#amount").val(ui.value);
        ajax({
              url: "/action",
              data: {parameter:ui.value},
            });
      },
   });
   $("#amount").val($("#slider-range-max").slider("value"));
});

主要.py

define("port", default=8888, help="run on the given port", type=int)
class Application(tornado.web.Application):
  def __init__(self):
     handlers = [
        (r"/", AuxHandler),
        (r"/action", MainHandler)
    ]
    settings = {
        "template_path": Settings.TEMPLATE_PATH,
        "static_path": Settings.STATIC_PATH,
    }

    tornado.web.Application.__init__(self, handlers, **settings)

class AuxHandler(tornado.web.RequestHandler):
  def get(self):
    self.render("index.html")

class MainHandler(tornado.web.RequestHandler):
  @asynchronous
  @tornado.gen.coroutine
  def get(self):
    speed = int(self.get_argument("parameter"))
    p=P()
    if speed > 1:
        p.startApp(speed)
    if speed<1:
        p.stopApp()

def main():
  tornado.options.parse_command_line()
  http_server = tornado.httpserver.HTTPServer(Application())
  http_server.listen(options.port)
  tornado.ioloop.IOLoop.instance().start()
if __name__ == "__main__":
  main()

和p.py

@tornado.gen.coroutine
def startApp(self,speed):
    x= yield print(speed)
    while True:
        yield x

在控制台我收到这个:

12
[I 160516 12:47:19 web:1946] 304 GET /action?parameter=12 (::1) 0.00ms
13
[I 160516 12:47:19 web:1946] 304 GET /action?parameter=13 (::1) 15.60ms
14
[E 160516 12:47:19 concurrent:336] Future <tornado.concurrent.Future object at 0x02FAA7D0> exception was never retrieved: Traceback (most recent call last):
  File "C:\Users\home\AppData\Local\Programs\Python\Python35-32\lib\site-packages\tornado\gen.py", line 1014, in run
    yielded = self.gen.throw(*exc_info)
  File "E:\work\python\Example2\p.py", line 11, in startApp
    x= yield print(speed)
  File "C:\Users\home\AppData\Local\Programs\Python\Python35-32\lib\site-packages\tornado\gen.py", line 1008, in run
    value = future.result()
  File "C:\Users\home\AppData\Local\Programs\Python\Python35-32\lib\site-packages\tornado\concurrent.py", line 232, in result
    raise_exc_info(self._exc_info)
  File "<string>", line 3, in raise_exc_info
  File "C:\Users\home\AppData\Local\Programs\Python\Python35-32\lib\site-packages\tornado\gen.py", line 1090, in handle_yield
    self.future = convert_yielded(yielded)
  File "C:\Users\home\AppData\Local\Programs\Python\Python35-32\lib\functools.py", line 743, in wrapper
    return dispatch(args[0].__class__)(*args, **kw)
  File "C:\Users\home\AppData\Local\Programs\Python\Python35-32\lib\site-packages\tornado\gen.py", line 1222, in convert_yielded
    raise BadYieldError("yielded unknown object %r" % (yielded,))
tornado.gen.BadYieldError: yielded unknown object None

我不知道如何处理这个“yielded unknown object None”错误，或者我的方法是否正确。任何想法都会非常有帮助。

Answer 1

异常来自 yield print(speed)。 print 返回 None，您不能输出 None。您只能产生 Futures 和类似的可等待对象，通常是在产生调用协程的结果时。参见 Refactoring Tornado Coroutines获取调用协程的指南。

如果你想打印速度的值，就这样做:

def startApp(self, speed):
    print(speed)