FilteredTopicWrapper

class lsst.ts.watcher.FilteredTopicWrapper(model, topic, filter_field)

Bases: object

Topic wrapper that caches data by the value of a filter field.

To make a topic wrapper call Model.make_filtered_topic_wrapper, instead of constructing a TopicWrapper directly. That allows using a cached instance, if available (and avoids a RuntimeError in the constructor, if an instance exists).

Parameters
modelModel

Watcher model. Used to add a TopicCallback to the topic, if one does not already exist.

topiclsst.ts.salobj.ReadTopic

Topic to read.

filter_fieldstr

Field to filter on. The field must be a scalar. It should also have a smallish number of expected values, in order to avoid caching too much data.

Raises
ValueError

If filter_field does not exist in the data, or if it exists but is an array.

RuntimeError

If this FilteredTopicWrapper already exists in the model. To avoid this, construct field wrappers by calling Model.make_filtered_field_wrapper.

Notes

A rule will typically use filtered _field_ wrappers (subclasses of BaseFilteredFieldWrapper) rather than FilteredTopicWrapper.

Filtered field wrappers are high-level objects that store data for a particular value of filter_field (e.g. a particular subsystem). FilteredTopicWrapper is lower level object that stores data for all values of filter_field (e.g. all subsystems).

Each BaseFilteredFieldWrapper contains a FilteredTopicWrapper.

Attributes
topiclsst.ts.salobj.ReadTopic

topic constructor argument.

filter_fieldstr

filter_field constructor argument.

descrstr

A short description of the wrapper.

data_cachestr

Dict of value of filter_field: most recent data seen for that value.

default_data

Default-constructed data. Use for validation of field wrappers.

call_eventasyncio.Event

An event that __call__ sets when it finishes. This is intended for use by unit tests.

Methods Summary

__call__(topic_callback)

Update the cached data.

add_field_wrapper(field_wrapper)

Add a filtered field wrapper to the internal cache.

get_data(filter_value)

Get the most recently seen data for the given filter_value, or None if no data seen.

Methods Documentation

__call__(topic_callback)

Update the cached data.

Set data_cache[filter_value] to the new data, and call update_value for each filtered field wrapper with the matching filter value.

Parameters
topic_callbackTopicCallback

The topic callback that triggered this call.

add_field_wrapper(field_wrapper)

Add a filtered field wrapper to the internal cache.

get_data(filter_value)

Get the most recently seen data for the given filter_value, or None if no data seen.

Parameters
filter_valuescalar

Value of filter_field for which to return data.