class Person:
    
    def __init__(self, name):
        self.name = name
        
    def greet(self):
        '''Print a greeting'''
        print('Hello, my name is ' + self.name)
        
    def __str__(self):
        return self.name
        

class Student(Person): # inherits from Person class
    
    def __init__(self, name):
        super().__init__(name)  # call the Person constructor
        self.courses = set()
    
    def add_course(self, course):
        self.courses.add(course)
    
    def courseload(self):
        '''Returns the student's number of courses.'''
        return len(self.courses)