def takeBlock(aList, row_l,row_r,col_l,col_r):
  """ Take sublist given from row row_l to row_r and column col_l to col_r from a double list.
  The convention for the index of the rows and columns are the same as in slicing.
  """
  result = []
  for aRow in aList[row_l:row_r]:
    result.append(aRow[col_l:col_r])
  return result