import os

class Student():
    def __init__(self, aNumber, aMentor):
        self._canSetMentor = None
        self._mentor = None
        self._number = None
        self._number = aNumber
        self._canSetMentor = True
        self.setMentor(aMentor)

    def getNumber(self):
        return self._number

    def getMentor(self):
        return self._mentor

    def hasMentor(self):
        has = not (self._mentor is None)
        return has

    def setMentor(self, aNewMentor):
        wasSet = False
        if not self._canSetMentor :
            return False
        self._canSetMentor = False
        self._mentor = aNewMentor
        wasSet = True
        return wasSet

    def delete(self):
        pass

    def __str__(self):
        return str(super().__str__()) + "[" + "number" + ":" + str(self.getNumber()) + "]" + str(os.linesep) + "  " + "mentor = " + ((format(id(self.getMentor()), "x")) if not (self.getMentor() is None) else "null")


class Mentor():
    def __init__(self, aName):
        self._name = None
        self._name = aName

    def getName(self):
        return self._name

    def delete(self):
        pass

    def __str__(self):
        return str(super().__str__()) + "[" + "name" + ":" + str(self.getName()) + "]"