openopc | OpenOPC for Python3.4

There's the library https://github.com/matzpersson/opc-rest-api From the description of the project:

Python Rest API using OpenOPC to provide direct API access for any OS platform. This proxy has to be installed on a Windows box with Python and OpenOPC installed to provide a API Gateway to other platforms.

The description is here http://headstation.com/archives/using-opc-rest-api/ From that it looks like you don't need to write the Rest API part yourself.

The library has been created by https://stackoverflow.com/users/6833456/matz see question OpenOPC Gateway Running use Client in OsX or Linux

This project on github adapts OpenOPC for Python 3.4 and newer. Try that.

That's because you are setting id=.

From the docs (emphasis mine):

Requesting properties for a single item returns a list of (id, description, value) tuples. Each tuple in the list represents a single property.

>>> opc.properties('Random.Int4')

[(1, 'Item Canonical DataType', 'VT_I4'), (2, 'Item Value', 491), (3, 'Item Quality', 'Good'), (4, ...

and:

The optional id parameter can be used to limit the returned value to that of a single property...

>>> opc.properties('Random.Int4', id=1)

'VT_I4'

A few things:

1. You never actually pass the UI to the function actualizarDatosOPC so it doesn't know it exists.

2. Is there any reason you can't use PyQt's built in threading tools? If you are going to use PyQt it might make sense to buy into the whole framework.

I suggest at least to add logging at the script level. You could also use custom Exit Codes from python so NSSM knows to report failure. Your failure would probably be when connecting to your services so, i.e. netowrk down or something so you could write custom exceptions for NSSM to restart. If it's running every 5 seconds you would probably know very soon.

Ensuring availability and avoiding crashes is about your code more than infrastructure, hence the above recommendations.

I believe using NSSM (for scheduling and such) is better than daemonizing, since you're basically adding functionality of NSSM in your script and potentially adding more code that may fail.