python代碼報錯 折騰半天了 萌新  求大佬為什么xianshi方法不起作用最后還報錯呢？ 用的是python2.7版本  嗚嗚嗚補(bǔ)充：class BankAcaunt:    def __init__(self, accauntname, accaunt):        self.accauntname = accauntname        self.accaunt = accaunt        self.blance = 0    def cunqian(self, qian):        self.blance = self.blance + qian        print qian    def quqian(self, fuqian):        self.blance = self.blance - fuqian        print fuqian    def xianshi(self):        print"the blance is", self.blance class InterestAccaunt(BankAcaunt):    def __init__(self, lixily):        self.lixily = float(lixily)    def zemgjia(self, year, lixi):        self.lixi = self.lixily * self.blance * year        print self.lixi     i = BankAcaunt(456, 789) i.cunqian(10) i.quqian(5) i.xianshi j = InteresAccaunt()補(bǔ)充：報錯圖 腦袋一團(tuán)漿糊補(bǔ)充：為什么會這樣啊