`repr` and operator overloading

Just to fill a gap, remember that Python allows for operator overloading. That is, you can override functions like __add__, __cmp__ etc. to provide support for such operators. For example:



In [1]:

    
class Student(object):
    def __init__(self, name, rollno, score):
        self.name = name
        self.rollno = rollno
        self.score = score

    def __repr__(self):
        return "%s (%s)" % (self.name, self.rollno)

    def __lt__(self, other):
        return self.score < other.score

s1 = Student('Adam', 'A1', 30)
s2 = Student('Bob', 'A2', 40)
s3 = Student('Carol', 'A3', 50)
print("Checking if %s has outscored %s..." % (s2, s1))
print(s1 < s2)
print("Checking if %s has outscored %s..." % (s2, s3))
print(s2 > s3)
print(sorted([s1, s3, s2]))









    



Checking if Bob (A2) has outscored Adam (A1)...
True
Checking if Bob (A2) has outscored Carol (A3)...
False
[Adam (A1), Bob (A2), Carol (A3)]

In the above, two special operators are being overridden.

One is the "less than" operator __lt__, that checks the score of students and allows for ordering based on that. This means that functions like sorted can be called without a special key! Note that you also get the __gt__ for free. What happens when two students have equal scores is left as an exercise.
The other operator is __repr__. That is called when a string operator is required. It is much better to override this, since that way, you can see a neat description of your object, rather than <__main__.Student instance at 0x7fdcdb58fc68>

__repr__ and operator overloading

`repr` and operator overloading