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$query = new EntityFieldQuery();

	$query->entityCondition('entity_type', 'node')
	->entityCondition('bundle', 'congressperson')
	->propertyCondition('status', 1);
	
	$result = $query->execute();
	
	if (!empty($result['node'])) {
		$nids = array_keys($result['node']);
	
		foreach ($nids as $nid) {
			$node = node_load($nid, NULL, TRUE);
		// do something awesome
						
/*
			unset($node->field_bioguide_id[$node->language][0]);
			unset($node->field_district[$node->language][0]);
			unset($node->field_state[$node->language][0]);
*/
/*
			$node->field_bioguide_id[$node->language][0]['value'] .= $bioguide;
			$node->field_district[$node->language][0]['value'] .= $district;	
*/
/*
			$node->field_state[$node->language][0]['value'] = $state;	
			$node->field_party[$node->language][0]['value'] = $party;	
*/		

			$node->field_chamber[$node->language][0]['value'] = $chambertitle;	
			
			// Make this change a new revision
			$node->revision = 1;
			$node->log = 'This node was programmatically updated at ' . date('c');
			
			node_save($node);
	
			}
	}