Get the value of multiple node at a time

[RYLF]

trafficstars

I found a get_node method, but I want to get more than one node at a time. Thank you.

[zerox1212]

Title says you want multiple values. Comment says you want multiple nodes?

At the moment I can only recommend that you write some simple functions in your user code which return lists of the items you want. Otherwise you need to explain more clearly what you are trying to do.

[oroulet]

If what you want is read value of many nodes at once, then you need to look at code of get_value() and make your own function. Should be very easy

[RYLF]

hi，this is my code .it can get a value of one node .
var = client.get_node("ns=x;s=xxx") print(var.get_data_value()) I want to get more than one node at a time. Do you have any related API?

For example, to get the ID list of node, and then return to the number of values in the node list at once? Thank

[harua8n]

@RYLF, try:

        params = ua.ReadParameters()
        for node_id_str in ['ns=x;s=xxx', 'ns=x;s=xxy']:
            nodeid = ua.NodeId.from_string(node_id_str)
            attr = ua.ReadValueId()
            attr.NodeId = nodeid
            attr.AttributeId = ua.AttributeIds.Value
            params.NodesToRead.append(attr)

        start = datetime.datetime.now()
        result = client.uaclient.read(params)
        print('Read delay : {}'.format((datetime.datetime.now() - start).total_seconds()))

[RYLF]

@harua8n Thank you. I'll try.

[Mounika-Thota]

Hi, I have used the above code i have did small modification to get 30 nodes and node values for every 2 seconds. i kept all 30 nodes in array and i used that array in the for loop while(1): params = ua.ReadParameters() for node_id_str in Array: nodeid = ua.NodeId.from_string(node_id_str) attr = ua.ReadValueId() attr.NodeId = nodeid attr.Value = nodeid.get_value() attr.AttributeId = ua.AttributeIds.Value params.NodesToRead.append(attr) print params time.sleep(2)

and the output is

ReadParameters(MaxAge:0, TimestampsToReturn:TimestampsToReturn.Source, NodesToRe ad:[ReadValueId(NodeId:StringNodeId(ns=2;s=173539328), AttributeId:AttributeIds. Value, IndexRange:None, DataEncoding:QualifiedName(0:None)), ReadValueId(NodeId: StringNodeId(ns=2;s=35129060), AttributeId:AttributeIds.Value, IndexRange:None, DataEncoding:QualifiedName(0:None)), ReadValueId(NodeId:StringNodeId(ns=2;s=3512 9060_-1), AttributeId:AttributeIds.Value, IndexRange:None, DataEncoding:Qualifi edName(0:None)), ReadValueId(NodeId:StringNodeId(ns=2;s=35129060-18), Attribut eId:AttributeIds.Value, IndexRange:None, DataEncoding:QualifiedName(0:None)), Re adValueId(NodeId:StringNodeId(ns=2;s=35129060-620), AttributeId:AttributeIds.V alue, IndexRange:None, DataEncoding:QualifiedName(0:None)), ReadValueId(NodeId:S tringNodeId(ns=2;s=35129060-110), AttributeId:AttributeIds.Value, IndexRange:N one, DataEncoding:QualifiedName(0:None)), ReadValueId(NodeId:StringNodeId(ns=2;s =35129060-111), AttributeId:AttributeIds.Value, IndexRange:None, DataEncoding: QualifiedName(0:None)), ReadValueId(NodeId:StringNodeId(ns=2;s=35129060-556), AttributeId:AttributeIds.Value, IndexRange:None, DataEncoding:QualifiedName(0:No ne)), ReadValueId(NodeId:StringNodeId(ns=2;s=35129060-108), AttributeId:Attrib uteIds.Value, IndexRange:None, DataEncoding:QualifiedName(0:None)), ReadValueId( NodeId:StringNodeId(ns=2;s=35129060-103), AttributeId:AttributeIds.Value, Inde xRange:None, DataEncoding:QualifiedName(0:None)), ReadValueId(NodeId:StringNodeI d(ns=2;s=35129060-996), AttributeId:AttributeIds.Value, IndexRange:None, DataE ncoding:QualifiedName(0:None)), ReadValueId(NodeId:StringNodeId(ns=2;s=35129060 -1004), AttributeId:AttributeIds.Value, IndexRange:None, DataEncoding:Qualified Name(0:None)), ReadValueId(NodeId:StringNodeId(ns=2;s=35129060-109), Attribute Id:AttributeIds.Value, IndexRange:None, DataEncoding:QualifiedName(0:None)), Rea dValueId(NodeId:StringNodeId(ns=2;s=35129060-3192), AttributeId:AttributeIds.V alue, IndexRange:None, DataEncoding:QualifiedName(0:None)), ReadValueId(NodeId:S tringNodeId(ns=2;s=35129060-734), AttributeId:AttributeIds.Value, IndexRange:N one, DataEncoding:QualifiedName(0:None)), ReadValueId(NodeId:StringNodeId(ns=2;s =35129060-1191), AttributeId:AttributeIds.Value, IndexRange:None, DataEncoding :QualifiedName(0:None)), ReadValueId(NodeId:StringNodeId(ns=2;s=35129060-987), AttributeId:AttributeIds.Value, IndexRange:None, DataEncoding:QualifiedName(0:N one)), ReadValueId(NodeId:StringNodeId(ns=2;s=35129060-106), AttributeId:Attri buteIds.Value, IndexRange:None, DataEncoding:QualifiedName(0:None)), ReadValueId (NodeId:StringNodeId(ns=2;s=35129060-3272), AttributeId:AttributeIds.Value, In dexRange:None, DataEncoding:QualifiedName(0:None)), ReadValueId(NodeId:StringNod eId(ns=2;s=35129060-3314), AttributeId:AttributeIds.Value, IndexRange:None, Da taEncoding:QualifiedName(0:None)), ReadValueId(NodeId:StringNodeId(ns=2;s=351290 60-3315), AttributeId:AttributeIds.Value, IndexRange:None, DataEncoding:Qualif iedName(0:None)), ReadValueId(NodeId:StringNodeId(ns=2;s=35129060-3316), Attri buteId:AttributeIds.Value, IndexRange:None, DataEncoding:QualifiedName(0:None)), ReadValueId(NodeId:StringNodeId(ns=2;s=35129060-3317), AttributeId:AttributeI ds.Value, IndexRange:None, DataEncoding:QualifiedName(0:None)), ReadValueId(Node Id:StringNodeId(ns=2;s=35129060-2998), AttributeId:AttributeIds.Value, IndexRa nge:None, DataEncoding:QualifiedName(0:None)), ReadValueId(NodeId:StringNodeId(n s=2;s=35129060-3267), AttributeId:AttributeIds.Value, IndexRange:None, DataEnc oding:QualifiedName(0:None)), ReadValueId(NodeId:StringNodeId(ns=2;s=35129060-_ 3268), AttributeId:AttributeIds.Value, IndexRange:None, DataEncoding:QualifiedNa me(0:None)), ReadValueId(NodeId:StringNodeId(ns=2;s=35129060_-_10), AttributeId: AttributeIds.Value, IndexRange:None, DataEncoding:QualifiedName(0:None))])

but i couldnt find any particular value for the node. when i see the same nodes in uaexpert we have few values .

how can i read the values ? please help

[oroulet]

@Mounika-Thota this seems to work perfectly this is a low leve ua api returning a low level ReadParameters structure. every structure contains a lot of things inclusing a list of ReadValueId containing the nodeid and and variant which itselv contains the python value... uexpert also displays all the paramter in your screenshot, not only the value

[Mounika-Thota]

Thank you for your reply. ReadValueId(NodeId:StringNodeId(ns=2;s=35129060-_3268), AttributeId:AttributeIds.Value, IndexRange:None, DataEncoding:QualifiedName(0:None))

if i want to have only node id and node value for the print statement what changes do i need to do? please help me. In the above output i couldnt see any value and there is only AttributeIds.Value which is constant for all nodes i want particular node value as mentioned in the previous comment in uaexpert. Please help me iam struck here.

[Mounika-Thota]

when i print RESULT i can see all the things that are in uaExpert , but how can i extract only value from all those parameters DataValue(Value:Variant(val:0,type:VariantType.Int32) value under DataValue--> Value-->Variant-->val how can i access this path?

[zerox1212]

You should probably search around the internet for basic python lessons. If you want to print only the value... then just print the value. You already have access to everything in the object. print(my_result.DataValue.Value.Variant.val)

OPC UA is built from many many complex object structures. You will often need to use an IDE that allows you to set break points so you can stop the code and inspect what objects you are dealing with.

[Mounika-Thota]

Iam able get the value. Thank you so much for your support.

[amisha218]

@Mounika-Thota Hey!!….Can you please help me to get the values of multiple tags/node at a time.

how did you resolve this issue??

[Keul125]

Thanks to @RYLF :

        tableau = []
        tableau.append('ns=3;s=Link_S7_1.db1280.12,b')
        tableau.append('ns=3;s=Link_S7_1.db1280.16,x5')
        params = ua.ReadParameters()
        for node_id_str in tableau:
            nodeid = ua.NodeId.from_string(node_id_str)
            attr = ua.ReadValueId()
            attr.NodeId = nodeid
            attr.AttributeId = ua.AttributeIds.Value
            params.NodesToRead.append(attr)

        start = datetime.datetime.now()
        result = client.uaclient.read(params)
        print('Read delay : {}'.format((datetime.datetime.now() - start).total_seconds()))
        for rep in result:
            # print(rep)
            print(rep.Value.Value)

Syntax for S7 data type: ,xN => Bit number N (ex: db1280.84,x0 ) ,b => byte ,c => char ,w => word ,i => int ,d => unsigned double word ,di => signed double word ,r => real/float

[vidyarao123]

Hi , To the same question, with the below code, I am able to write for 1 tag at a time. Is it possible to write for multiple tags at the same time ?

name = "PYTHON_OPCUA_SERVER" addspace = server.register_namespace(name) node = server.get_objects_node() Param = node.add_object(addspace, "Parameters") Temp = Param.add_variable(addspace, "Temperature", 0) Temp.set_value(2)

[AndreasHeine]

sure! client.set_values()

https://github.com/FreeOpcUa/python-opcua/blob/0d595e596c9922699f0b36abb79583d5763eeb9b/opcua/client/client.py#L666

[vidyarao123]

But I am trying from the server side

[AndreasHeine]

unfortunately we only provide a highlevelmethod on clientside because its part of the spec.!

this is actually only a conviniencefunction (at leat in my eyes)... you could try to make a localhost client connection to the server and use the request but then it must be writeable from clientside and is i would assume not more performant then looping over a list and write each item. on serverside there should not be an major delay!