Unfortunately I don't think this is a good way to make this visible -- it will only be available in the shell. How about the following approach:

* Create an enum called StorageLevel in Python (e.g. using these options: http://stackoverflow.com/questions/36932/how-can-i-represent-an-enum-in-python)
* In RDD.persist(), translate the Python StorageLevel object, which is just an identifier, to a Java one, using a hashmap that you initialize inside SparkContext (when you're connected to Java).