pubsub2.py

# Use a single global message broker for all topics
_global_message_broker = MessageBroker()


def publish(topic, value):
    """Publishes a value on a topic for a subscriber to receive"""
    _global_message_broker.publish(topic, value)


def subscribe(topic, callback):
    """Subscribes to a topic.
    The subscriber callback is called with the topic value whenever
    the a value is published to that topic, and with the initial
    value if there is one.
    """
    _global_message_broker.subscribe(topic, callback)


def unsubscribe(topic, callback):
    """Unsubscribe from a topic.
    The topic and callback must have previously be passed to 'subscribe'.
    """
    _global_message_broker.unsubscribe(topic, callback)