PyOPC is a Python Library implementing the XML - Data Access Protocol Version 1.01 (XML-DA 1.01) by the OPC Foundation. PyOPC supports easy creation of XMLDA compliant clients and servers without having to deal with the SOAP protocol and server issues.
Very light and worked out-of-the-box for me. I only have one issue with HTTP authentication, currently I had to disable it in IIS. If someone has a workaround for that, I would be very grateful.