Examples for OPC client and subscriber development in Python are now on GitHub: github.com/OPCLabs/Examples-QuickOPC-Python .

Note: QuickOPC now supports Python in much better way, cleaner syntax, and public packages (pypi.org/project/opclabs-quickopc/) on Python Package Index . See What's new in QuickOPC 2023.2 for more information. And, over 270 examples are available in the User's Guide!

Great, thanks for letting me know.

Yes, definitely. Unless there are some "hidden" problems that we do not know about yet, with pythonnet you get at least three advantages:

1) Cleaner architecture (and a chance for better performance) - the unnecessary COM layer in between QuickOPC and Python goes away.
2) Cleaner and shorter syntax.
3) Ability to use more features of QuickOPC (not everything is directly exposed in COM - but everything in available in .NET).

Best regards

Hello.
So, in the example you posted, you are actually not using the extension methods approach, you are using the "core" ReadMultiple methods. That is fine too, of course.

I do not quite understand your question. What do you mean by that you "have to" do it this way? Have you tried the shorter syntax (and if so, what was the code and what was the problem), or do you know the shorter syntax at all?

Best regards

Thank you - I think you are making progress!
And, most likely I know what is causing your problem.

The EasyUAClient object actually only has a handful methods on it - those that do the "core" work. The remaining methods are implement as so-called extension methods over the IEasyUAClient interface that EasyUAClient implements. The extension methods are not methods on EasyUAClient or IEasyUAClient. They are actually static methods on an "unrelated" class, and the IEasyUAClient interface needs to be passed to them as an addition first argument. C# and VB.NET can make the extension methods "appear" as if they were true methods on the object or interface, but most likely pythonnet cannot do that.

Look here: opclabs.doc-that.com/files/onlinedocs/QuickOpc/Latest/User%2...c.UA.EasyUAClient_members.html

You will find that for reading, there is only the ReadMultiple method listed under "Public Methods". The ReadValue method you are trying to use, and many other ReadXXXX methods, are listed under "Extension Methods". All these other methods simply transform the inputs and outputs of the ReadMultiple method, but otherwise they do the same thing (reading), so there is no reason for them to exist on the IEasyUAClient interface. And, if you click on the ReadValue method link, it will lead you here:

opclabs.doc-that.com/files/onlinedocs/QuickOpc/Latest/User%2...ClientExtension~ReadValue.html

From there, you can see how you will need to call the ReadValue method in pythonnet: You need to figure out how to call static methods on IEasyUAClientExtension class. I can see something about it, with an example, right here: pythonnet.github.io/ .

You will then then pass in your "client" variable as an additional first argument.

Note: I could not read what is in the image you have attached, it is blurred, but it probably is not needed at this moment..

Best regards

Hello.

Thank you for pointing the attention to pythonnet. I was not aware of this tool. From my point of view, in principle that should be definitely much better approach, even better than going through COM (pywin32). But, as opposed to pywin32, we have not tried or tested with pythonnet at all yet. So I cannot guarantee whether it will work or well.

Since this looks like a nice tool, at some we will look at it and if it works, even provide some guidance and example. But cannot do that right now - there is other development work ongoing. If you want to try it out, you will be more than welcome!

Regarding your other question which seems to be involved with the performance: Getting value at rates like 100 milliseconds is definitely achievable - but you also need to tell how many such items you will monitor, because the more items the more bandwidth & other resources are needed.

You can use the trial version to test out everything upfront.

Best regards