This function is used in Python Scripting.


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.


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

  • Parameters

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
Code Snippet
# This example will get user-specified attributes over a period of time from a Matrikon OPC HDA explorer.
# Declare start and end dates
start =, 10, 24)
end =, 10, 24)

# Call the system function
hda = system.opchda.readAttributes('Matrikon HDA','1',[1],start,end)
print hda

system opchda readAttributes, opchda.readAttributes