As an introduction to sorting lists in Python you'll have to implement two functions.

In this exercise we represent students as a pair of (mark, full_name), so a tuple of two elements.

And in this exercises we represent students as lists of pairs, like:

>>> students = [(85, "Susan"), (6, "Joshua"), (37, "Jeanette")]

Part 1

Write a function named sort_by_mark that take as argument a list of students and returns a copy of it sorted by mark in descending order. Such as:

>>> sort_by_mark(students)
[(85, "Susan"), (37, "Jeanette"), (6, "Joshua")]

Part 2

Write a function named sort_by_name that take as argument a list of students and returns a copy of it sorted by name in ascending order, such as:

>>> sort_by_name(students)
[(37, "Jeanette"), (6, "Joshua"), (85, "Susan")]

Advices

Take a look at the Sorting howto.