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.match(str(val)) 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, this):
        #if Token.NUMBER.match(str(this.val)):
        print(this.val)
        #    return int(this.val)
        if this.val == Token.OPERAND_ADDITION:
            return this.evalue(this.gauche) + this.evalue(this.droite)
        elif this.val == Token.OPERAND_MULTIPLICATION:
            return this.evalue(this.gauche) * this.evalue(this.droite)
        else:
            return int(this.val)

    def __str__():
        pass

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