class ValueLastMatchFeature(object):
"""Extract transient feature from previous event"""
def __init__(self, field_name, entity_field, feature_name):
self.field_name = field_name
self.entity_field = entity_field
self.feature_name = feature_name
self.state_manager = StateManager()
def initialise_state(self, entity_id):
"""Sum and count state initiated as 0. and 0."""
self.state_manager.write(entity_id, None)
def get_feature_names(self):
"""Return feature name"""
return [self.feature_name]
def pre_extraction_update(self, event):
pass
def extract_feature_dict(self, event):
# if state missing, initialise state
entity_id = event[self.entity_field]
if self.state_manager.entity_missing(entity_id):
self.initialise_state(entity_id)
return {self.feature_name: self.state_manager.read(entity_id)}
def post_extraction_update(self, event):
self.state_manager.write(event[self.entity_field],
event[self.field_name])
