Python基础的练习

Question

可能重复的问题：
Python基础第8章项目3

嗨，我是一个刚开始学习Python的新手程序员。
我之前也问过同样的问题，并且已经解决了，但我的答案并不完全符合问题的要求。

我需要帮助，想知道为什么我需要实现一个新方法，尽管我可以用其他方式来完成。

谢谢！

问题：

Bank类的__str__方法返回一个包含账户的字符串，但这些账户是随机顺序的。请设计并实现一个更改，使得账户按照名字的顺序放入字符串中。
[这是我不理解的部分]
(提示：你还需要在SavingsAccount类中定义一个新方法。)

class Bank(object):

    def __init__(self):
        self._accounts = {}
    def __str__(self):
        """Return the string rep of the entire bank."""
        pTemp =[]
        for i in xrange(len(SavingsAccount.temp)-1):
            if self._accounts.get(SavingsAccount.temp[i]).getName() >= self._accounts.get(SavingsAccount.temp[i+1]).getName():
                temp = SavingsAccount.temp[i]
                SavingsAccount.temp[i] = SavingsAccount.temp[i+1]
                SavingsAccount.temp[i+1] = temp
        for i in SavingsAccount.temp:
            pTemp.append(self._accounts[i])
        return '\n'.join(map(str, pTemp))

    def add(self, account): 
        """Inserts an account using its PIN as a key."""
        self._accounts[account.getPin()] = account
    def remove(self, pin):
        return self._accounts.pop(pin, None)
    def get(self, pin):
        return self._accounts.get(pin, None)
    def computeInterest(self):
        """Computes interest for each account and 
        returns the total."""
        total = 0.0
        for account in self._accounts.values():
            total += account.computeInterest()
        return total

class SavingsAccount(object):
    """This class represents a Savings account
    with the owner's name, PIN, and balance."""
    RATE = 0.02
    temp = []
    def __init__(self, name, pin, balance = 0.0):
        self._name = name
        self._pin = pin
        self._balance = balance
        SavingsAccount.temp.append(self)
    def __str__(self):
        result =  'Name:    ' + self._name + '\n' 
        result += 'PIN:     ' + self._pin + '\n' 
        result += 'Balance: ' + str(self._balance)
        return result
    def getBalance(self):
        return self._balance
    def getName(self):
        return self._name
    def getPin(self):
        return self._pin
    def deposit(self, amount):
        """Deposits the given amount and returns the
        new balance."""
        self._balance += amount
        return self._balance
    def withdraw(self, amount):
        """Withdraws the given amount.
        Returns None if successful, or an
        error message if unsuccessful."""
        if amount < 0:
            return 'Amount must be >= 0'
        elif self._balance < amount:
            return 'Insufficient funds'
        else:
            self._balance -= amount
            return None
    def computeInterest(self):
        """Computes, deposits, and returns the interest."""
        interest = self._balance * SavingsAccount.RATE
        self.deposit(interest)


def main():
    bank = Bank()
    bank.add(SavingsAccount("Zelda","1003",5000.00))
    bank.add(SavingsAccount("Wilma","1001",4000.00))
    bank.add(SavingsAccount("Fred","1002",1000.00))
    print bank

main()

面向对象编程字符串处理方法重载编程逻辑数据排序类和对象问题解决新手编程

Python基础的练习

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