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Connectomes are stored as scipy.sparse.csc_matrix objects in .npz format.

To read in python:

from scipy import sparse
M = sparse.load_npz('MOs_right_ALL_INPUTS_ipsi.csc.npz')

Each such connection matrix will have a shape of N x M, where N is the total number of neurons in the model (almost 10 million) and M is the number of neurons in the target region (depends on that region). This means that the first axis denotes the presynaptic neuron and the second axis the postsynaptic neuron.

Each matrix file is accompanied by a file that specifies the global indices of the target neurons, i.e. the indices of the same neurons along the first axis. It contains a nympy array of length M in .npy format. It can be used for example to find the connectivity originating form the same neurons in a different matrix and will be required to assemble a full N x N matrix.

To read in python:

import numpy
idx = numpy.load('MOs_right_ALL_INPUTS_indices.npy')