@giampaolo:

> Maybe something like this instead?
>      SharedMemory(name=None, attach_if_exists=False, size=0)

I think this misses the use case when wanting to ensure we only attach to an existing shared memory block and if it does not exist, we should raise an exception because we can not continue.  (If the shared memory block should already be there but it is not, this means something bad happened earlier and we might not know how to recover here.)

I believe the two dominant use cases to address are:
1) I want to create a shared memory block (either with or without a pre-conceived name).
2) I want to attach to an existing shared memory block by its unique name.