PdCom5 Subscriber

class pdcom5.Transmission(period)

Specifies how a variable is transferred to the client.

Parameters

period (datetime.timedelta) – Periodic transmission.

class pdcom5.SubscriberBase(process, transmission: pdcom5._PdComWrapper.Transmission)
newValues(autoclose=True) → AsyncGenerator[datetime.timedelta, Any]

Entry point for library users to process incoming data.

Changed in version 5.3: Use generator instead of context manager.

This function returns an asynchronous generator. In the body of the async for loop, the values of the subscriptions assigned to this subscriber are guaranteed to not change. If you break out of the loop early, all subscriptions are cancelled automatically, unless autoclose is set to False.

Parameters

autoclose – Close connections when leaving the loop, defaults to True

The following example shows how to subscribe to two variables with a period of one second.

import pdcom5
process = pdcom5.Process()
await process.connect("msr://localhost")
subscriber = process.create_subscriber(1.0)
cos = await subscriber.subscribe("/osc/cos")
sin = await subscriber.subscribe("/osc/sin")
async for timestamp in subscriber.newValues():
    print(f"At {timestamp}, cos was {cos.value}" +
            f" and sin was {sin.value}.")

Please do not do any blocking operations in the body of the loop, like sleeping for a long time. The reason is that the library has to cache the incoming values to make sure no data is skipped. Also, using the same subscription in multiple concurrent tasks is not allowed, for the same reason. Just create one subscriber per task.

If you want to reuse existing subscriptions and break out of the loop early, pay attention to close the generator fully before reusing. This can be done using a try...finally block or by using contextlib.aclosing.

timestamp_gen = subscriber.newValues(autoclose=False)
try:
    async for timestamp in timestamp_gen:
        process(timestamp)
        break
finally:
    await timestamp_gen.aclose()
    # subscriber.newValues() can now be called again
class pdcom5.Subscriber(process, transmission: pdcom5._PdComWrapper.Transmission)

Variable subscriber.

This class manages how variables are subscribed and the callback when new values are received.

Parameters

  • process – Process instance

  • transmission – Kind of subscription (poll, event based, periodic)

async subscribe(variable: Union[str, pdcom5._PdComWrapper.Variable], selector: Optional[pdcom5._PdComWrapper.Selector] = None) → pdcom5.Subscription.Subscription

Subscribe to a variable.

Parameters

  • variable – Variable to subscribe.

  • selector – Optional selector to create a view on multidimensional data.

Returns

a Subscription instance.