Python websocket 对象没有属性"write_message"错误

Question

我从这里得到了python websocket客户端的示例代码，我在下面遇到了一个问题。我编辑了这段代码，从原来的几个地方，因为我遇到了一个问题:

• 删除connect方法并将其合并到构造函数中。我是的自我。未发现_ws_connection问题。

• 修改WebSocketClient __init__()方法接受'url'并删除了''参数。我不确定""的传递是什么意思。

Problem1:

Traceback (most recent call last):
  File "websocketcli.py", line 138, in <module>
    main()
  File "websocketcli.py", line 129, in main
    client.send('Hello world!')
  File "websocketcli.py", line 49, in send
    self._ws_connection.write_message(escape.utf8(json.dumps(data)))
  File "/users/anjangam/pyvenv/venv/lib/python2.7/site-packages/tornado/websocket.py", line 970, in write_message
    return self.protocol.write_message(message, binary)
AttributeError: 'NoneType' object has no attribute 'write_message'

问题2:当我从wssocketclient构造函数中删除"*"时，我得到以下错误，几乎与问题1中遇到的错误相同。注意:我使用的是python 2.7.8版本。

Traceback (most recent call last):
  File "websocketcli.py", line 138, in <module>
    main()
  File "websocketcli.py", line 129, in main
    client.send('Hello world!')
  File "websocketcli.py", line 52, in send
    self._ws_connection.write_message(escape.utf8(json.dumps(data)))
  File "/users/anjangam/pyvenv/venv/lib/python2.7/site-packages/tornado/websocket.py", line 970, in write_message
    return self.protocol.write_message(message, binary)
AttributeError: 'NoneType' object has no attribute 'write_message'

客户机代码:

from tornado import escape
from tornado import gen
from tornado import httpclient
from tornado import httputil
from tornado import ioloop
from tornado import websocket
import functools
import json
import time

APPLICATION_JSON = 'application/json'
DEFAULT_CONNECT_TIMEOUT = 60
DEFAULT_REQUEST_TIMEOUT = 60

class WebSocketClient():
"""Base for web socket clients.
"""
def __init__(self, connect_timeout=DEFAULT_CONNECT_TIMEOUT,
             request_timeout=DEFAULT_REQUEST_TIMEOUT):
    self.connect_timeout = connect_timeout
    self.request_timeout = request_timeout
def connect(self, url):
    """Connect to the server.
    :param str url: server URL.
    """
    headers = httputil.HTTPHeaders({'Content-Type': APPLICATION_JSON})
    request = httpclient.HTTPRequest(url=url,
                                     connect_timeout=self.connect_timeout,
                                     request_timeout=self.request_timeout,
                                     headers=headers)
    self._ws_connection = websocket.WebSocketClientConnection(ioloop.IOLoop.current(),
                                                  request)
    self._ws_connection.connect_future.add_done_callback(self._connect_callback)
    print 'Connection: ', self._ws_connection
    def send(self, data):
        """Send message to the server
        :param str data: message.
        """
        if not self._ws_connection:
            raise RuntimeError('Web socket connection is closed.')
        self._ws_connection.write_message(escape.utf8(json.dumps(data)))
    def close(self):
        """Close connection.
        """
        if not self._ws_connection:
            raise RuntimeError('Web socket connection is already closed.')
        self._ws_connection.close()
    def _connect_callback(self, future):
        if future.exception() is None:
            self._ws_connection = future.result()
            self._on_connection_success()
            self._read_messages()
        else:
            self._on_connection_error(future.exception())
    @gen.coroutine
    def _read_messages(self):
        while True:
            msg = yield self._ws_connection.read_message()
            if msg is None:
                self._on_connection_close()
                break
            self._on_message(msg)
    def _on_message(self, msg):
        """This is called when new message is available from the server.
        :param str msg: server message.
        """
        pass
    def _on_connection_success(self):
        """This is called on successful connection ot the server.
        """
        pass
    def _on_connection_close(self):
        """This is called when server closed the connection.
        """
        pass
    def _on_connection_error(self, exception):
        """This is called in case if connection to the server could
        not established.
        """
        pass

class TestWebSocketClient(WebSocketClient):
    def __init__(self, url):
        WebSocketClient.__init__(self, url)
    def _on_message(self, msg):
        print(msg)
        deadline = time.time() + 1
        ioloop.IOLoop().instance().add_timeout(
            deadline, functools.partial(self.send, str(int(time.time()))))
    def _on_connection_success(self):
        print('Connected!')
        self.send(str(int(time.time())))
    def _on_connection_close(self):
        print('Connection closed!')
    def _on_connection_error(self, exception):
        print('Connection error: %s', exception)

def main():
    client = TestWebSocketClient()
    client.connect('ws://localhost:8888/ws')
    client.send('Hello world!')

    try:
        ioloop.IOLoop.instance().start()
    except KeyboardInterrupt:
        client.close()

if __name__ == '__main__':
    main()

Answer 1

你引用的原始代码在python 3.5上工作得很好，但是我怀疑你正在使用python 2的某个版本。它会中断的原因可能是由于您提到的星号，这不是python 2的特性。PEP 3102讨论了这一点，但简而言之，星号只会强制函数调用传递关键字参数，而不是依赖于参数提供的顺序。

以以下函数为例:

# we can use positional arguments on this one
def test(a, b):
    print(a, b)
# this will require keyword arguments to be supplied on function calls
def test_keywords_args_required(*, a, b):
    print(a, b)
test(1, 2) # test can be called using positional arguments
test_keywords_args_required(1, 2) # this will error out. Needs keywords args!
test_keywords_args_required(a=1, b=2) # this will work!

如果您使用该链接最初提供的代码，并删除星号，代码应该可以工作(与python 2.7确认)。