BaseTopic¶

class lsst.ts.salobj.topics.BaseTopic(*, salinfo, name, sal_prefix)¶

Bases: abc.ABC

Base class for topics.

Parameters:	salinfo : `SalInfo` SAL component information name : `str` Topic name, without a “command_” or “logevent_” prefix. sal_prefix : `str` SAL topic prefix: one of “command_”, “logevent_” or “”
Raises:	RuntimeError If the topic cannot be constructed.
Attributes:	salinfo : `SalInfo` The `salinfo` constructor argument. name : `str` The `name` constructor argument. sal_name : `str` The topic name used by SAL. For example: “logevent_summaryState”. log : `logging.Logger` A logger. volatile : `bool` Is this topic volatile (in which case it has no historical data)? attr_name : `str` Name of topic attribute in `Controller` and `Remote`. For example: “evt_summaryState”. rev_code : `str` Revision hash code for the topic. This code changes whenever the schema for the topic changes, and it is part of the DDS topic name. For example: “90255bf1” dds_name : `str` Name of topic seen by DDS. For example: “Test_logevent_summaryState_90255bf1”.

Attributes Summary

`DataType`	The type (class) for a message of this topic.
`metadata`	Get topic metadata as a `TopicMetadata`, if available, else `None`.

Attributes Documentation

DataType¶

The type (class) for a message of this topic.

When you read or write a message for this topic you are reading or writing an instance of DataType.

Notes

The preferred way to write a message for a topic is:

RemoteCommand.set_start to start a command.
CommandEvent.set_put to write an event.
CommandTelemetry.set_put to write a telemetry message.

However, it is also possible to use DataType to create a message, then write, it as separate operations. For example, assuming we have a Remote for SAL component “Test”:

# The preferred way to issue a command:
await = remote.cmd_wait.set_put(duration=2, timeout=5)

# But an alternative is to first create the command,
# then send it, as two separate operations:
message = remote.cmd_wait.DataType(duration=2)
await remote.cmd_wait.start(message, timeout=5)

# Or, even more verbosely:
message = remote.cmd_wait.DataType()
message.duration = 2
await remote.cmd_wait.start(message, timeout=5)

metadata¶: Get topic metadata as a TopicMetadata, if available, else None.

Navigation

BaseTopic¶