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Lightstreamer Client SDK

Project description

Lightstreamer Python Client SDK

Lightstreamer Python Client SDK enables any Python application to communicate bidirectionally with a Lightstreamer Server. The API allows to subscribe to real-time data pushed by the server and to send any message to the server.

The library offers automatic recovery from connection failures, automatic selection of the best available transport, and full decoupling of subscription and connection operations. It is responsible of forwarding the subscriptions to the Server and re-forwarding all the subscriptions whenever the connection is broken and then reopened.

Installation

You can install the Lightstreamer Client SDK from PyPI:

python -m pip install lightstreamer-client-lib

The sdk is supported on Python 3.9 and above.

Quickstart

To connect to a Lightstreamer Server, a LightstreamerClient object has to be created, configured, and instructed to connect to the Lightstreamer Server. A minimal version of the code that creates a LightstreamerClient and connects to the Lightstreamer Server on https://push.lightstreamer.com will look like this:

from lightstreamer_client import *

client = LightstreamerClient("http://push.lightstreamer.com/","DEMO")
client.connect()

For each subscription to be subscribed to a Lightstreamer Server a Subscription instance is needed. A simple Subscription containing three items and two fields to be subscribed in MERGE mode is easily created (see Lightstreamer General Concepts):

sub = Subscription("MERGE",["item1","item2","item3"],["stock_name","last_price"])
sub.setDataAdapter("QUOTE_ADAPTER")
sub.setRequestedSnapshot("yes")
client.subscribe(sub)

Before sending the subscription to the server, usually at least one SubscriptionListener is attached to the Subscription instance in order to consume the real-time updates. The following code shows the values of the fields stock_name and last_price each time a new update is received for the subscription:

class SubListener:
  def onItemUpdate(self, update):
    print("UPDATE " + update.getValue("stock_name") + " " + update.getValue("last_price"))

  # other methods...

sub.addListener(SubListener())

Below is the complete Python code:

from lightstreamer_client import *

sub = Subscription("MERGE",["item1","item2","item3"],["stock_name","last_price"])
sub.setDataAdapter("QUOTE_ADAPTER")
sub.setRequestedSnapshot("yes")

class SubListener:
  def onItemUpdate(self, update):
    print("UPDATE " + update.getValue("stock_name") + " " + update.getValue("last_price"))
  def onListenStart(self, aSub):
    pass
  def onClearSnapshot(self, itemName, itemPos):
    pass
  def onCommandSecondLevelItemLostUpdates(self, lostUpdates, key):
    pass
  def onCommandSecondLevelSubscriptionError(self, code, message, key):
    pass
  def onEndOfSnapshot(self, itemName, itemPos):
    pass
  def onItemLostUpdates(self, itemName, itemPos, lostUpdates):
    pass
  def onListenEnd(self, subscription):
    pass
  def onListenStart(self, subscription):
    pass
  def onSubscription(self):
    pass
  def onSubscriptionError(self, code, message):
    pass
  def onUnsubscription(self):
    pass
  def onRealMaxFrequency(self, frequency):
    pass

sub.addListener(SubListener())

client = LightstreamerClient("http://push.lightstreamer.com","DEMO")
client.subscribe(sub)
client.connect()

Logging

To enable the internal client logger, create a LoggerProvider and set it as the default provider of LightstreamerClient.

loggerProvider = ConsoleLoggerProvider(ConsoleLogLevel.DEBUG)
LightstreamerClient.setLoggerProvider(loggerProvider)

Compatibility

Compatible with Lightstreamer Server since version 7.2.0.

Documentation

Support

For questions and support please use the Official Forum. The issue list of this page is exclusively for bug reports and feature requests.

License

Apache 2.0

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