system.opchda.readAttributes

This function is used in Python Scripting.

Description

Reads the specified attributes for the given item over a time range. Attributes and their IDs are defined in the OPC-HDA specification, and can be discovered by calling system.opchda.getAttributes().

Client Permission Restrictions

This scripting function has no Client Permission restrictions.

Syntax

system.opchda.readAttributes(serverName, itemId, attributeIds, startDate, endDate)

Parameters

Type	Parameter	Description
String	serverName	The name of the defined OPC-HDA server to read.
String	itemId	The itemID to retrieve attributes for.
List[String]	attributeIds	The integer IDs of the attributes to read. The attribute ids are defined in the OPC-HDA specification. The attributes can also be obtained by calling system.opchda.getAttributes(). Some servers may not support all attributes.
String (can be other data types, such as int)	startDate	The starting date/time of the query.
String (can be other data types, such as int)	endDate	The ending date/time of the query.

Returns

List[ReadResults] - A list of read results which is one-to-one with the requested attributes. The ReadResult object has a serviceResult quality property that indicates whether the call was successful, and it is itself a list of QualifiedValues.

Scope

Gateway, Vision Client, Perspective Session

Code Examples

Example #1

# This example will get user-specified attributes over a period of time from a Matrikon OPC HDA explorer.
# Declare start and end dates
start = system.date.getDate(2022, 10, 24)
end = system.date.getDate(2022, 10, 24)
 
# Call the system function
hda = system.opchda.readAttributes('Matrikon HDA','1',[1],start,end)
print hda