Why can't I import xyz IDL data definition from abc IDL namespace?

There are a few possibilities:

• The Python CORBA stubs for your IDL interface are not in your $PYTHONPATH environment variable
• Another set of Python CORBA stubs are superceding the stubs you are interested in using. There is a very high probability this is the case if the IDL module (i.e., namespace) your IDL interface is defined in is reopened in other ALMA CVS modules and you are using < ACS 4.1.4. See ALMASW2002083 in the ALMA SPR system for more details
• You are importing an IDL module which provides definitions used by another IDL module you have already imported. For some reason or another omniORBPy restricts users from doing this. Don't worry if this sounds confusing, it is. An example should help:

     import ACS
     import Control #the Control IDL module includes IDL files which utilize the "ACS" IDL module

is OK, while there's a strong possibility:

     import Control
     import ACS

will throw an exception after the import ACS statement.

• you've defined module xyz in IDL where xyz is a reserved keyword in Python. Look at the IDL->Python CORBA Mapping Specifications available from OMG's website to determine what Python module xyz gets mapped to.

How you import your IDL interfaces has a great impact on which interfaces are available in your IDL module (namespace). If you have not previously imported the IDL module but you request one of its interfaces, the interface loading code will create the IDL (namespace) module for you and populate it with the information from that single interface. Subsequent interface loads will add to this dynamically created IDL (namespace) module. Depending on how many interfaces you load and their dependencies, you may end up with a IDL (namespace) module that contains a small subset of the interfaces.

The fix for this problem is to reload the IDL (namespace) module. This action will force all of the interfaces in the module to be loaded from disk.

To illustrate the fix, here is an example. Suppose the code that is failing in your program looks like this:

    myModule = __import__("Module", globals(), locals(), ["MyClass"])
    myClass = myModule.__dict__.get("MyClass")  # Returns None because "Module" isn't completely loaded
    myObject = myClass() # Fails because instance is None

You can force Module to be reloaded by doing the following:

    myModule = __import__("Module", globals(), locals(), ["MyClass"])
    myClass = myModule.__dict__.get("MyClass")  # Returns None because "Module" isn't completely loaded
    if myClass is None:
        reload(myModule)  # Reloads "Module" from the file system
        myClass = myModule.__dict__.get("MyClass")  # Returns "MyClass" if it is defined in the "Module" 
    myObject = myClass() # Works now