Macro expansion: intercept statement interpretation

[Benjamin Niemann]

You could try to override __import__ to first parse the source for macro 
definitions and do the expansions. Usage would then be:

import DoMagicWithImportModule
import ModuleWithMacros

(Your code wouldn't work, because python throws a SyntaxError long 
before it even tries to execute 'import MyCustomMacroLib')
The code at http://docs.python.org/lib/examples-imp.html could be 
extended to first read the contents of the module (after find_module) 
and passes the expanded source (e.g. as a StringIO) to load_module.

This has of course the problem (that many implementations of macro 
expansion share) that line numbers in exception dumps have not much 
relation to lines of the unexpanded code...