s6.py

class Student:
    def __init__(self,name,rollno,grade):
        self.name=name
        self.rollno=rollno
        self.grade=grade
    def __repr__(self):
        return f"{self.name}-{self.rollno}-{self.grade}"
        


#Initializing Student Objects
s1=Student("karthi",15,"second")
s2=Student("Indhu",12,"fifth")
s3=Student("Sarvesh",21,"first")


#Creating list of student objects
s4=[s1,s2,s3]

#Sorting list of objects
#Deifining function which will return rollno of the object
def sort_key(s):
    return s.rollno
  
  
#sorting list of objects without specifying key parameter.It raises TypeError
print (sorted(s4))  
#Output:TypeError: '<' not supported between instances of 'Student' and 'Student'


#Sorting list of objects based on attribute:rollno
s5=sorted(s4,key=sort_key) 
print (s5)   
#Output:[Indhu-12-fifth, karthi-15-second, Sarvesh-21-first]