# Streaming

`Stream` allows filtering and sampling of realtime Tweets using Twitter’s API.

Streams utilize Streaming HTTP protocol to deliver data through an open, streaming API connection. Rather than delivering data in batches through repeated requests by your client app, as might be expected from a REST API, a single connection is opened between your app and the API, with new results being sent through that connection whenever new matches occur. This results in a low-latency delivery mechanism that can support very high throughput. For further information, see https://developer.twitter.com/en/docs/tutorials/consuming-streaming-data

## Using `Stream`

To use `Stream`, an instance of it needs to be initialized with Twitter API credentials (Consumer Key, Consumer Secret, Access Token, Access Token Secret):

    import tweepy

    stream = tweepy.Stream(
      "Consumer Key here", "Consumer Secret here",
      "Access Token here", "Access Token Secret here"
    )

Then, `Stream.filter()` or `Stream.sample()` can be used to connect to and run a stream:

    stream.filter(track=["Tweepy"])

Data received from the stream is passed to `Stream.on_data()`. This method handles sending the data to other methods based on the message type. For example, if a Tweet is received from the stream, the raw data is sent to `Stream.on_data()`, which constructs a `Status` object and passes it to `Stream.on_status()`. By default, the other methods, besides `Stream.on_data()`, that receive the data from the stream, simply log the data received, with the logging level dependent on the type of the data.

To customize the processing of the stream data, `Stream` needs to be subclassed. For example, to print the IDs of every Tweet received:

    class IDPrinter(tweepy.Stream):

        def on_status(self, status):
            print(status.id)

    printer = IDPrinter(
      "Consumer Key here", "Consumer Secret here",
      "Access Token here", "Access Token Secret here"
    )
    printer.sample()

## Threading

Both `Stream.filter()` and `Stream.sample()` have a `threaded` parameter. When set to `True`, the stream will run in a separate thread, which is returned by the call to either method. For example:

    thread = stream.filter(follow=[1072250532645998596], threaded=True)

## Handling Errors

`Stream` has multiple methods to handle errors during streaming. `Stream.on_closed()` is called when the stream is closed by Twitter. `Stream.on_connection_error()` is called when the stream encounters a connection error. `Stream.on_request_error()` is called when an error is encountered while trying to connect to the stream. When these errors are encountered and `max_retries`, which defaults to infinite, hasn’t been exceeded yet, the `Stream` instance will attempt to reconnect the stream after an appropriate amount of time. By default, all three of these methods log an error. To customize that handling, they can be overridden in a subclass:

    class ConnectionTester(tweepy.Stream):

        def on_connection_error(self):
            self.disconnect()

`Stream.on_request_error()` is also passed the HTTP status code that was encountered. The HTTP status codes reference for the Twitter API can be found at https://developer.twitter.com/en/support/twitter-api/error-troubleshooting.

`Stream.on_exception()` is called when an unhandled exception occurs. This is fatal to the stream, and by default, an exception is logged.