Huge Graph Structure
Sounds like you need a database and an iterator over the results. Then you wouldn't have to keep it all in memory at the same time but you could always have access to it.
I'm developing an application in which I need a structure to represent a huge graph (between 1000000 and 6000000 nodes and 100 or 600 edges per node) in memory. The edges representation will contain some attributes of the relation. 
I have tried a memory map representation, arrays, dictionaries and strings to represent that structure in memory, but these always crash because of the memory limit.
I would like to get an advice of how I can represent this, or something similar.
By the way, I'm using python.