PubNub Python SDK

The Native implementation uses the requests library. It supports both synchronous and asynchronous execution patterns:

Synchronous calls

Use the sync() method. This returns an Envelope object which wraps both the Result and the Status. Exceptions are raised natively using the raise Exception syntax.

Asynchronous calls

Use the async() function. You must pass a callback function which will be invoked with either a response or an error.

# Example of the conceptual pattern for async calls
pubnub.async(callback_function, ...)

Python Versions

Supported versions: 3.7, 3.8, 3.9, 3.10.

Platforms

• Ubuntu: Primary supported platform (tested via Travis.CI).
• Windows/MacOS/BSD: Support has been verified, but newer releases have not been explicitly tested on these platforms.

To initialize the PubNub client, create a PNConfiguration object, set your subscribe_key, publish_key, and a unique uuid, then pass this configuration to the PubNub class.

pnconfig = PNConfiguration()

pnconfig.subscribe_key = 'mySubscribeKey'
pnconfig.publish_key = 'myPublishKey'
pnconfig.uuid = 'myUniqueUUID'
pubnub = PubNub(pnconfig)

Integrate the PubNub Python SDK into your project using pip.

pip install pubnub

This example demonstrates how to use the PubNub Python SDK with asyncio to subscribe to a channel and listen for messages.

To run the example, you need to install the required dependencies and set your PubNub credentials as environment variables. For testing purposes, the demo keys can be used.

Prerequisites:

• asyncio
• pubnub

Setup steps:

1. Install dependencies using pip.
2. Export PUBNUB_PUBLISH_KEY and PUBNUB_SUBSCRIBE_KEY.
3. Execute the main.py script.

pip install asyncio pubnub
export PUBNUB_PUBLISH_KEY=demo
export PUBNUB_SUBSCRIBE_KEY=demo
python main.py

By default, daemon mode is disabled for all requests. When disabled, asynchronous requests will block the main thread until all child processes/threads are closed. To enable Java-like behavior—where the program can continue execution without waiting for response completion—explicitly set daemon to True in the PubNub configuration.

pubnub.config.daemon = True

Publishing a message

Use the .publish() method to send data to a channel. You can use .pn_async(callback) to provide a callback function that handles the result or error via an envelope and status object.

Subscribing to channels

Use the .subscribe() method to listen for messages on specific channels using .channels('channel_name') and call .execute() to start the subscription.

Note: The status object in the publish callback provides an is_error() method to check for success.

def my_publish_callback(envelope, status):
  if status.is_error():
    ... #handle error here
  else:
    ... #handle result here

pubnub.publish().channel('my_channel').message('Hello world!').pn_async(my_publish_callback)

pubnub.subscribe().channels('my_channel').execute()

You can trigger a message to be received by an AsyncIO subscriber by using a curl command to hit the PubNub REST API publish endpoint. This is useful for testing subscriptions without writing a separate publisher script.

Use the following format: curl "https://ps.pndsn.com/publish/${PUBNUB_PUBLISH_KEY}/${PUBNUB_SUBSCRIBE_KEY}/0/${CHANNEL}/0/%22${MESSAGE}%22"

export PUBNUB_PUBLISH_KEY=demo
export PUBNUB_SUBSCRIBE_KEY=demo
curl "https://ps.pndsn.com/publish/${PUBNUB_PUBLISH_KEY}/${PUBNUB_SUBSCRIBE_KEY}/0/my_channel/0/%22Hello%20World%22"

The SDK supports the asyncio library. There are two ways to invoke calls:

1. Using result(): Returns only the result. If an exception occurs, it is raised natively.
2. Using future(): Returns an Envelope (a wrapper for the result and status). In the event of an exception, you can check the status using the env.is_error() method.