sort key python

1#1 Changes list
2list.sort(reverse=True)
3#2 Returns sorted list
4sorted(list, reverse=True)

1>>> student_tuples = [
2...     ('john', 'A', 15),
3...     ('jane', 'B', 12),
4...     ('dave', 'B', 10),
5... ]
6>>> sorted(student_tuples, key=lambda student: student[2])   
7# sort by age
8[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
9

1>>> sorted(student_tuples, key=itemgetter(2))
2[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
3

1>>> student_tuples = [
2...     ('john', 'A', 15),
3...     ('jane', 'B', 12),
4...     ('dave', 'B', 10),
5... ]
6>>> sorted(student_tuples, key=lambda student: student[2])   # sort by age
7[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
8

1>>> class Student:
2...     def __init__(self, name, grade, age):
3...         self.name = name
4...         self.grade = grade
5...         self.age = age
6...     def __repr__(self):
7...         return repr((self.name, self.grade, self.age))
8

1>>> student_objects = [
2...     Student('john', 'A', 15),
3...     Student('jane', 'B', 12),
4...     Student('dave', 'B', 10),
5... ]
6>>> sorted(student_objects, key=lambda student: student.age)   # sort by age
7[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
8