How do we sort a list of objects based on multiple parameters in python

Question

So my class is

class Student:
        
    raise_amt = 1.8
    no_of_students = 0
    def __init__(self, id, name, age, salary):
        self.id = id
        self.name = name
        self.age = age
        self.salary = salary
        
        
        Student.no_of_students+=1
        
    
    def __repr__(self):
        return "Student({}, {}, {}, {})".format(self.id, self.name, self.age, self.salary)
    
    
    def __str__(self):
        return "Student user: {}, name:{}, age:{}".format(self.id, self.name, self.age)

And I have created an object with 3 objects

s1 = Student(10, "Pranav", 21, 1200)
s2 = Student(20, "Pranav", 22, 1500)
s3 = Student(30, "tejas", 22, 5999)

students = []

students.append(s1)
students.append(s2)
students.append(s3)

The sort function given is

students.sort(key = lambda x:x.name)

I WANT TO SORT THE LIST IN SUCH A WAY THAT IF NAMES ARE EQUAL, IT SHOULD THEN CHECK AGE AND IF THAT IS EQUAL ASWELL THEN SALARY

Basically the equivalent of the comparator class in Java

Already answered here https://stackoverflow.com/questions/4233476/sort-a-list-by-multiple-attributes — Hirusha Fernando, Dec 18 '20 at 10:10

Arty · Accepted Answer · 2020-12-18T10:12:22.027

0

To achieve what you want just return sorting key as a tuple of necessary fields:

students.sort(key = lambda x: (x.name, x.age, x.salary))

Try full working code here online .

edited Dec 18 '20 at 10:12

answered Dec 18 '20 at 10:06

Arty

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score 0 · Answer 2 · answered Dec 18 '20 at 10:40

The best way is to implement magic methods like __gt__ (https://docs.python.org/3/reference/datamodel.html#object.__gt__) in your class and let the standard operators do what they are supposed to do. The standard sort function will work like a charm letting the objects know how to compare themselves.

How do we sort a list of objects based on multiple parameters in python

2 Answers2