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这是我的代码：

class Category():

    
    def __init__(self,category,balance=0,ledger=[]):
        self.category = category
        self.balance = balance
        self.ledger = ledger

    def check_funds(self,amt):
        if amt > self.balance:
            return False
        else:
            return True
    

    def deposit(self, dep_amt, description=""):
        self.balance +=dep_amt
        dep_note = "{\"amount\": "+str(dep_amt)+", \"description\": "+description+"}"
        self.ledger.append(dep_note)
        
    def withdraw(self, wd_amt, description=""):
        if not self.check_funds(wd_amt):
            return False
        else:
            self.balance -= wd_amt
            wd_note = "{\"amount\": "+"-"+str(wd_amt)+", \"description\": "+description+"}"
            self.ledger.append(wd_note)
            return True
        
    def get_balance(self):
        return self.balance
    
    def transfer(self,tf_amt,category):
        wd_description = "Transfer to "+category.category
        dp_description = "Transfer from "+self.category
        self.withdraw(tf_amt,wd_description)
        category.deposit(tf_amt,dp_description)

创建实例：

food = Category('food')
food.deposit(1000,"food initial deposit")
food.withdraw(300,"groceries")

clothing = Category('clothing')
clothing.deposit(1000,"clothes initial deposit")
clothing.withdraw(20,"pants")
food.transfer(200,clothing)

运行代码时，clothing.ledger这是输出：

['{"amount": 1000, "description": 食品初始押金}', '{"amount": -300, "description": 杂货}', '{"amount": 1000, "description": 衣服初始deposit}', '{"amount": -20, "description": 裤子}', '{"amount": -200, "description": 转入衣物}', '{"amount": 200, "description "：从食物转移}']

这就是我要找的：

['{"amount": 1000, "description": 衣服初始存款}', '{"amount": -20, "description": 裤子}', '{"amount": -200, "description": 转账去衣服}']

基本上我的分类帐属性采用所有我不想要的实例。

4

1 回答 1

1

在 Python 中传递动态或可变（列表、字典）默认值时，最好将它们设置为None并在函数内指定它们的预期值。

def __init__(self,category,balance=0,ledger=None):
    If ledger is None:
        ledger = []
    self.category = category
    self.balance = balance
    self.ledger = ledger

否则账本只会被评估一次。参考：https ://medium.com/python-features/how-to-avoid-classic-pitfall-while-passing-default-values-in-python-7002c0dc4c7c

于 2021-02-23T23:12:02.327 回答