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Global OPC XML-DA options

Python dictionaries are used to represent global options. As denoted above, these dictionaries can then be used as parameters for OPC operations. However, often it is handy to define default global options that are used all over the application. For instance, it may make sense to define a server-specific default ``MaxAge'' option, which is automatically assigned to all according SOAP messages.

Therefore PyOPC allows to specify these global options at the creation of the client or server object, such as shown in listing 3. These global options will then be used for all operations, unless they are overridden by global options in the method parameters.

\begin{lstlisting}[caption={Assigning Global Options to a PyOPC
Client Instance...
... ReturnItemName=True,

The PyOPC framework always checks if global options, which are passed as method parameters, can be applied to the current OPC operation. If an option is unknown or misspelled, a Python TypeError will be raised. This way, errors due to accidental misspellings or improper use of options are prevented.

Hermann Himmelbauer 2006-11-07