Accessing one element of an array

[Oassal]

Hello!

I am trying to write on specific addresses in an array (i have a node that has an array of ~16,000 integers and i am only interested in some of them), after doing some research, i found that a possible solution is to pass indexRange in the writing service, however, i could not find anything related to that in python-opcua documentation/examples

Is that parameter available in python-opcua? If it is not, do you have any ideas?

Thanks alot 😄

[schroeder-]

If you switch to asyncua you can use
async def read_attribute(self, attr, indexrange=None, raise_on_bad_status=True):

[Oassal]

Thanks for the suggestion, i succsefully read/wrote the values of the whole array but i couldn't access a specific one

I used the following syntax :
await var.write_attribute(ua.AttributeIds.Value,new_value,indexrange="1")

to change the second element of the following array:

The result : it replaces the whole array with a single integer:

Any ideas ?

[schroeder-]

I didn't use index range, so i can help here. Some servers may not handle index range and ignore it.

[eduardo-leite-oliveira]

Hi Oassal,

Could you help me on how did you read the values of the whole array?

[Oassal]

Hello @eduardo-leite-oliveira,

You can simply read the whole array by using the same syntax used for reading simple variables :

        client=Client(url)
        client.connect()
        Array = client.get_node("ns= 1; i=1") #the array is represented by the namespace ns= 1 and has the identifier 1

I hope this helped