################### ## # ## classloader.py # ## # ################### import sys, types def _get_mod(modulePath): try: aMod = sys.modules[modulePath] if not isinstance(aMod, types.ModuleType): raise KeyError except KeyError: # The last [''] is very important! aMod = __import__(modulePath, globals(), locals(), ['']) sys.modules[modulePath] = aMod return aMod def _get_func(fullFuncName): """Retrieve a function object from a full dotted-package name.""" # Parse out the path, module, and function lastDot = fullFuncName.rfind(u".") funcName = fullFuncName[lastDot + 1:] modPath = fullFuncName[:lastDot] aMod = _get_mod(modPath) aFunc = getattr(aMod, funcName) # Assert that the function is a *callable* attribute. assert callable(aFunc), u"%s is not callable." % fullFuncName # Return a reference to the function itself, # not the results of the function. return aFunc def _get_class(fullClassName, parentClass=None): """Load a module and retrieve a class (NOT an instance). If the parentClass is supplied, className must be of parentClass or a subclass of parentClass (or None is returned). """ aClass = _get_func(fullClassName) # Assert that the class is a subclass of parentClass. if parentClass is not None: if not issubclass(aClass, parentClass): raise TypeError(u"%s is not a subclass of %s" % (fullClassName, parentClass)) # Return a reference to the class itself, not an instantiated object. return aClass ###################### ## Usage ## ###################### class StorageManager: pass class StorageManagerMySQL(StorageManager): pass def storage_object(aFullClassName, allOptions={}): aStoreClass = _get_class(aFullClassName, StorageManager) return aStoreClass(allOptions)