I have a PR at https://github.com/numpy/numpy/pull/8443 that proposes to
change the value of the offset attribute of memmap objects. At the
moment it is not the offset into the memmap file (as the docstring would
lead you to believe) but this modulo mmap.ALLOCATIONGRANULARITY.
It was deemed best to double-check on the mailing list whether anyone
could think of a good reason why this is the case and/or whether anyone
was using this property of the offset attribute.
If you have comments about this proposed change, it is probably best if
you do it on the PR in order to keep the discussion all in the same place.