How do I perform secondary sorting in python?

Question

If i have a list of numbers [4,2,5,1,3] I want to sort it first by some function f and then for numbers with the same value of f i want it to be sorted by the magnitude of the number.

This code does not seem to be working.

list5 = sorted(list5)
list5 = sorted(list5, key = lambda vertex: degree(vertex)) 

Secondary sorting first: list5 is sorted based on magnitude. Primary sorting next: list5 is sorted based on some function of the numbers.

Answer 1

From the Python 3 docs on sorting

from operator import itemgetter, attrgetter
student_objects = [
    Student('john', 'A', 15),
    Student('jane', 'B', 12),
    Student('dave', 'B', 10),
]
student_tuples = [
    ('john', 'A', 15),
    ('jane', 'B', 12),
    ('dave', 'B', 10),
]

#The operator module functions allow multiple levels of sorting. For example, to sort by grade then by age:

sorted(student_tuples, key=itemgetter(1,2))
sorted(student_objects, key=attrgetter('grade', 'age'))

Answer 2

On a phone, but youcan sort by tuple.

sorted(list5, lambda x: (degree(x),x))

Don't forget the reverse flag if you need it.

Answer 3

This is how I would do.

s = ['a', 'ac', 'b', 'ab']
s.sort(key=lambda x: (x[0], x[1]) if len(x)>1 else (x[0],))

Result:

['a', 'ab', 'ac', 'b']