python类问题

Question

class BankAccount:
""" Class definition modeling the behavior of a simple bank account """

def __init__(self, initial_balance):
    """Creates an account with the given balance."""
    …
def deposit(self, amount):
    """Deposits the amount into the account."""
    …
def withdraw(self, amount):
    """
    Withdraws the amount from the account.  Each withdrawal resulting in a
    negative balance also deducts a penalty fee of 5 dollars from the balance.
    """
    …
def get_balance(self):
    """Returns the current balance in the account."""
    …
def get_fees(self):
    """Returns the total fees ever deducted from the account."""
    …

The deposit and withdraw methods each change the account balance. The withdraw method also deducts a fee of 5 dollars from the balance if the withdrawal (before any fees) results in a negative balance. Since we also have the method get_fees, you will need to have a variable to keep track of the fees paid.

Here's one possible test of the class. It should print the values 10 and 5, respectively, since the withdrawal incurs a fee of 5 dollars.

my_account = BankAccount(10)
my_account.withdraw(15)
my_account.deposit(20)
print my_account.get_balance(), my_account.get_fees()