gistfile1.py

import numpy

# load a 10k x 10k array (800MB) previously stored with
# numpy.save('/tmp/x.npy', numpy.random.rand(10000, 10000))
shared = [numpy.load('/tmp/x.npy', mmap_mode='r') for _ in range(10)]

# touch all elements in all 10 copies of the same mmap'ed array
print [x.sum() for x in shared]
# ...resident/real mem spikes at 10x 800MB, nothing shared?