import re

class Token:
    OPERAND_ADDITION = "+"
    OPERAND_MULTIPLICATION = "*"
    NUMBER = re.compile(r'\d+') #CHANGER

class Expression:

    def __init__(self, val, gauche=None, droite=None):
        if Token.NUMBER.search(str(val)) is not None and (gauche != None or droite != None):
            raise AttributeError("gauche et droite ne peuvent pas exister si val est un nombre")
        self.val = val
        self.gauche = gauche
        self.droite = droite

    def evalue(self):
        if self.val == Token.OPERAND_ADDITION:
            return self.gauche.evalue() + self.droite.evalue()
        elif self.val == Token.OPERAND_MULTIPLICATION:
            return self.gauche.evalue() * self.droite.evalue()
        else:
            return int(self.val)

    def __str__(self):
        if Token.NUMBER.match(string=self.val) is not None:
            return self.val
        return "(" + self.gauche.__str__() + self.val + self.droite.__str__() + ")"
        

exp = Expression('*',
Expression(6, None, None),
Expression('+',
Expression(4, None, None),
Expression(3, None, None)
))
print(exp.evalue())
print(str(exp))