Question

我在使用我试图制作的Python程序创建对象时遇到了问题。我不熟悉课程，所以不确定这是否是一个明显的问题。

我有两个班级：

class transaction():


    def __init__(self, amount, name, typ, bank, date):
        self.amount = Decimal(amount)
        self.name = name
        self.type = typ
        self.bank = bank
        self.date = date
        self.day = date[8:]
        self.month = date[5:7]
        self.year = date[:4]

    def compare(self, other_trans):

        result = True

        for attrib in other_trans.__dict__.keys():
            if other_trans.__getattribute__(attrib) != self.__getattribute__(attrib):
                result = False
                break

        return result


class full_date():
    transactions = []
    def __init__(self, lst, date):
        for trans in lst:
            if trans.date == date:
                self.transactions.append(trans)
        self.date = date
        true_list = self.transactions[:]
        duplicate = True
        indexer = 0
        while duplicate:
            duplicate = False
            for trans2 in self.transactions[indexer:]:
                indexer = self.transactions.index(trans2)
                testlist = self.transactions[:]
                del testlist[testlist.index(trans2)]
                for point in testlist:
                    if point.compare(trans2):
                        duplicate = True
                        del true_list[true_list.index(point)]
                        break
                    else:
                        duplicate = False
                if duplicate:
                    break
            self.transactions = true_list

transaction应该是可操作的分析对象（金融交易），而full_date是存储这些交易的对象。我在理论上知道我可以用字典做到这一点，但我用这个作为学习如何使用类的练习，__init__函数给了我一个很好的方法来清理重复的事务。

但是，由于某些未知原因，当我尝试创建full_date类的多个实例时，它们只是复制自己，所以我最终得到的对象完全相同。

以下是我的尝试：

>>> y = transaction("12.51", "Amazon", "Other", "HSBC", "2014-12-06")
>>> x = transaction("12.49", "Amazon", "Other", "HSBC", "2014-12-06")
>>> w = transaction("12.50", "Amazon", "Other", "HSBC", "2014-12-06")
>>> lst = [w,x,y,z]
>>> b = full_date(lst, "2014-12-06") #a populated list so b.transactions should be populated
>>> b.transactions #and is
[<__main__.transaction object at 0x7fbcc37e5bd0>, <__main__.transaction object at 0x7fbcbf3a3e10>, <__main__.transaction object at 0x7fbcc37e5c10>]
>>> a = full_date([], "2014-12-06") #an empty list so a.transactions shouldn't be populated
>>> a.transactions #but it is
[<__main__.transaction object at 0x7fbcc37e5bd0>, <__main__.transaction object at 0x7fbcbf3a3e10>, <__main__.transaction object at 0x7fbcc37e5c10>]

当我在定义对象后尝试清除对象时，也会发生这种情况：

>>> b = None
>>> b = full_date([], "2014-12-05") #an empty list so b.transactions should be empty - also has the wrong date to make it more confusing
>>> b.transactions #but it is
[<__main__.transaction object at 0x7fbcc37e5bd0>, <__main__.transaction object at 0x7fbcbf3a3e10>, <__main__.transaction object at 0x7fbcc37e5c10>]

有谁知道为什么会这样？

编辑：找到答案。

class full_date:
    def __init__(self, args):
        self.transactions = []
        ... code

而不是：

class full_date:
    transactions = []
    def __init__(self, args):
        ... code

Python复制对象？

0 个答案: