Someone

sparse_matrix, these_links, last_link_from = [], [1], 1for link_from, link_to in wikipedia_links:    if link_from != last_link_from:        sparse_matrix.append(these_links)        while link_from != last_link_from+1:            sparse_matrix.append([])            last_link_from += 1        these_links = [int(link_from)]    if link_to <= wikipedia_links[-1][0]-1:        these_links.append(int(link_to))    last_link_from = link_from