无法在继承的类中使用属​​性

Question

When creating an object of this type:

from tweepy.streaming import StreamListener
from tweepy import OAuthHandler
from tweepy import Stream
class listener(StreamListener):

    def __init__(self, consumer_key, consumer_secret, access_token, access_token_secret, a):
        StreamListener.__init__(self)
        self.auth = OAuthHandler(consumer_key, consumer_secret)
        self.auth.set_access_token(access_token, access_token_secret)
        self.stream = Stream(self.auth, self)
        self.stream.filter(track=tweet_filter.strip().split())
        self.a = 2

        print access_token

    def on_data(self, data):
        data_decoded = json.loads(data)
        body = data_decoded['text'].encode('utf-8')
        print self.a

if __name__ == '__main__':
    # parse input arguments

    t_listener = listener(consumer_key=params["consumer_key"],
                          consumer_secret=params["consumer_secret"],
                          access_token=params["access_token"],                                  access_token_secret=params["access_token_secret"],
                          a=3)

I don't see access_token printed out, and I also get the error message

'listener' object has no attribute 'a'

Answer 1

self.stream.filter() never returns. It is the point at which the Tweepy API calls out to Twitter, and in a loop receives the twitter stream for your listener to handle. You can't create the stream inside the listener initialiser, as the stream needs the listener to be fully created before it can start.

Simply don't put Stream() handling in the listener. Handle that separately and pass in your StreamListener() instance outside of the __init__ method.

If your listener must have access to the API, just pass it in; the original StreamListener.__init__() method accepts an api argument:

from tweepy.streaming import StreamListener
from tweepy import API
from tweepy import OAuthHandler
from tweepy import Stream

class listener(StreamListener):
    def __init__(self, api=None, a=None):
        StreamListener.__init__(self, api=api)
        self.a = a

    def on_data(self, data):
        data_decoded = json.loads(data)
        body = data_decoded['text'].encode('utf-8')
        print self.a

if __name__ == '__main__':
    # parse input arguments
    auth = OAuthHandler(params["consumer_key"], params["consumer_secret"],)
    auth.set_access_token(access_token=params["access_token"], params["access_token_secret"])
    api = tweepy.API(auth)

    listener = listener(api, 3)
    stream = Stream(self.auth, listener)
    stream.filter(track=tweet_filter.strip().split())