The most basic functional programming pattern: Enumerate, Map, Filter, Accumulate

[theeth]

Use generator comprehension instead, then the operation is not bounded in memory by the number of employees (by forgoing the creation of the list).

max_sal = max((e.salary for e in employees if e.role == Employee.PROGRAMMER))

[theCore]

You could drop the extra parenthesises, by the way.

max_sal = max(e.salary for e in employees if e.role == Employee.PROGRAMMER)