from random import choice

class Student:
    
    def __init__(self, first_name, last_name):
        self.first_name = first_name
        self.last_name = last_name
        self.grades = []

    @property
    def full_name(self):
        return f'{self.first_name} {self.last_name}'

    @property
    def email(self):
        return f'{self.first_name}{self.last_name[0]}@codewars.com'

    def add_grade(self, grade):
        self.grades.append(grade)
        
    @property
    def grade_average(self):
        if not self.grades:
            return 0
        return sum(self.grades) / len(self.grades)
    
    def assess(self):
        if not self.grades:
            return 'Ungraded'
        
        avg = self.grade_average
        if 0 <= avg <= 25:
            return 'B-'
        elif 25 < avg <= 50:
            return 'B+'
        elif 50 < avg <= 75:
            return 'A-'
        elif 75 < avg <= 100:
            return 'A+'
            
    def add_random_grade(self):
        random_grade = choice(range(1, 11))
        self.grades.append(random_grade)