>>> from pensions import put_average

>>> lpens = [['1111A', 68, 640, 589, 574],
...          ['2222D', 69, 710, 550, 570, 692]]
>>> a = put_average (lpens)
>>> lpens
[['1111A', 68, 640, 589, 574, 601.0], ['2222D', 69, 710, 550, 570, 692, 630.5]]