records_array = array([1, 2, 3, 1, 1, 3, 4, 3, 2])
idx_sort = argsort(records_array)
sorted_records_array = records_array[idx_sort]
vals, idx_start, count = unique(sorted_records_array, return_counts=True,
    return_index=True)
res = split(idx_sort, idx_start[1:])
vals = vals[count > 1]
res = [x for x in res if x.size > 1]
Get a list of all indices of repeated elements in a numpy array