首先,这是我的测试代码,我使用的是python 3.2.x:
class account:
def __init__(self):
pass
class bank:
def __init__(self):
self.balance = 100000
def balance(self):
self.balance
def whitdraw(self, amount):
self.balance -= amount
def deposit(self, amount):
self.balance += amount
当我做:
a = account()
a.bank.balance
我希望得到平衡值的回报,而不是我得到的功能“平衡”,为什么会这样?我这样做时会返回余额值:
class bank:
def __init__(self):
self.balance = 100000
def balance(self):
self.balance
def whitdraw(self, amount):
self.balance -= amount
def deposit(self, amount):
self.balance += amount
a = bank()
a.balance
所以我想知道为什么会这样,如果有人想出办法让我在嵌套版本中获得平衡价值,那就太棒了。
我的代码版本,带有注释:
#
# 1. CamelCasing for classes
#
class Account:
def __init__(self):
# 2. to refer to the inner class, you must use self.Bank
# 3. no need to use an inner class here
self.bank = self.Bank()
class Bank:
def __init__(self):
self.balance = 100000
# 4. in your original code, you had a method with the same name as
# the attribute you set in the constructor. That meant that the
# method was replaced with a value every time the constructor was
# called. No need for a method to do a simple attribute lookup. This
# is Python, not Java.
def withdraw(self, amount):
self.balance -= amount
def deposit(self, amount):
self.balance += amount
a = Account()
print(a.bank.balance)
有几个问题:
balance
。return
的balance()
声明。balance()
在bank
的一个实例上运作。在a.bank.balance
中没有实例:在这里,a.bank
指的是内部类本身。a.bank
是类(不是实例),因为你从来没有在a
上创建一个银行实例。因此,如果a.bank
是一个类,a.bank.balance
是一个绑定到该类的方法。
但这有效:
class account:
def __init__(self):
self.bank = account.bank()
class bank:
def __init__(self):
self.balance = 100000
def whitdraw(self, amount):
self.balance -= amount
def deposit(self, amount):
self.balance += amount
a = account()
print a.bank.balance
当然,当您显示没有嵌套类的工作代码时,它确实引出了为什么要为此使用嵌套类的问题。我认为非嵌套版本更清晰。