Question about Objects/MyObject/MyVariable from example

[GronbergInfo]

Hi have this on a plc with opc ua enabled.

Would Objects be "root", MyObject = "Python" and MyVariable = "ManualEnabled" ?

When i run from the example:
_logger.info("Children of root are: %r", await client.nodes.root.get_children())
The result i get is:
INFO:asyncua:Children of root are: [Node(NodeId(Identifier=85, NamespaceIndex=0, NodeIdType=<NodeIdType.TwoByte: 0>)), Node(NodeId(Identifier=86, NamespaceIndex=0, NodeIdType=<NodeIdType.TwoByte: 0>)), Node(NodeId(Identifier=87, NamespaceIndex=0, NodeIdType=<NodeIdType.TwoByte: 0>))]

[AndreasHeine]

that looks strange! you usually only have one root node...

what did you expect? kind of not understand your question!?

[AndreasHeine]

ok! how can i help?

[GronbergInfo]

ok! how can i help?

I am trying to figure out how to access these variables in the python script i am making.

inthe example its written like this:

       # Now getting a variable node using its browse path
        myvar = await client.nodes.root.get_child(["0:Objects", "2:MyObject", "2:MyVariable"])
        obj = await client.nodes.root.get_child(["0:Objects", "2:MyObject"])

And im not sure which and what to change to access my current single variable.

[AndreasHeine]

get_child makes a BrowseRequest for HierarchicalReferences of the Node (client.nodes.root) you are calling it on. It returns a Node-Class-Instance if the BrowsePath (["0:Objects", "2:MyObject", "2:MyVariable"]) is valid in the OPC UA Servers Addressspace! However you can use different approaches "get_children()" returns all Nodes with HierarchicalReferences to that Node. And if you want to access the value you can just simply use the methods of the Node-Class e.g. "read_value()" (

opcua-asyncio/asyncua/common/node.py

Line 39 in db9e81d

class Node:

)

here is a small tutorial https://github.com/AndreasHeine/opcua-tutorial its not officially part of this repo its still "WIP" maybe some day ^^

[GronbergInfo]

Now getting a variable node using its browse path

    myvar = await client.nodes.root.get_child(["0:Objects", "2:MyObject", "2:MyVariable"])

Thanks, after some digging around and reading "all over" the place, i managed to get this:

async def main():
    url = "opc.tcp://192.168.8.81:48020/"
    async with Client(url=url) as client:
        var = client.get_node("ns=4;i=2002")
        print(" --- myvar ---")
        myvar = client.get_node("ns=4;s=Root.Python.ManualEnabled")

        _logger.info("myvar is: %r", myvar)

    print("Value: ", await myvar.read_value()) # returns just the Value
        print("DataValue: ", await myvar.read_data_value()) # returns the DataValue (Value + StatusCode + Timestamps)
        print("BrowseName: ", await myvar.read_browse_name()) # returns the BrowseName ("0:ServiceLevel")
        print("DataType: ", await myvar.read_data_type()) # returns the DataType of the Value (i=3 -> Byte)
        print("DisplayName: ", await myvar.read_display_name()) # returns the DisplayName in form of LocalizedText

which in its turn i get this in the console:

 --- myvar ---
Value:  True
DataValue:  DataValue(Value=Variant(Value=True, VariantType=<VariantType.Boolean: 1>, Dimensions=None, is_array=False), StatusCode_=StatusCode(value=0), SourceTimestamp=datetime.datetime(2022, 7, 14, 9, 10, 16, 734289), ServerTimestamp=None, SourcePicoseconds=None, ServerPicoseconds=None)
BrowseName:  QualifiedName(NamespaceIndex=4, Name='ManualEnabled')
DataType:  NodeId(Identifier=1, NamespaceIndex=0, NodeIdType=<NodeIdType.TwoByte: 0>)
DisplayName:  LocalizedText(Locale=None, Text='ManualEnabled')

This is getting me plenty of the way, to read the values, i have tested and the Value changes from True to False according to what i have in the PLC.

Thank you.

[AndreasHeine]

Your welcome!