应该是空字符串的内容添加了一个值

Question

well I'm doing a free code camp project and something quite strange is happening to me a function works perfectly with an object instance and fails with another one creating instead of an empty string a string with a value that I had used before but I don't know what could be the cause I leave below the whole code but where you should pay attention is in line 25 which is the one that causes the error the related functions are withdraw I leave the whole code because by executing so many functions I assumed that the error could come from another so I wanted to make sure that the info is complete.

def withdraw(self, amount, cause=False):
    if self.check_funds(amount):
        amount = amount * -1
        if cause:
            self.ledger.append('"amount" : ' + str(amount) + ' "description" : ' + str(cause))
            self.value += amount
            print(self.ledger)
            return True
        else:
            self.ledger.append('') # line 25
            return True

whole code below

class Category:
    def __init__(self, categorie):
        self.categorie = categorie
        self.value = 0
        self.ledger = []
        print ("el objeto "+ categorie + " ha sido creado")

    def deposit(self, amount, cause=False):
        if cause:
            self.ledger.append('"amount" : ' + str(amount) + ' "description" : ' + str(cause))
            self.value += amount
            print(self.ledger)
        else:
            self.ledger.append('')
        
    def withdraw(self, amount, cause=False):
        if self.check_funds(amount):
            amount = amount * -1
            if cause:
                self.ledger.append('"amount" : ' + str(amount) + ' "description" : ' + str(cause))
                self.value += amount
                print(self.ledger)
                return True
            else:
                self.ledger.append('')
                return True   
        else:
            return False


    def get_balance(self):
        return self.value

    def check_funds(self, amount):
        if amount > self.value:
            return False
        else:
            return True

    def transfer(self, amount, category):
        if self.check_funds(amount):
            category.deposit(amount, "Transfer from " + self.categorie)
            self.withdraw(amount, "Transfer to " + category.categorie)
            return True
        else:
            return False

    def __str__(self):
        asterisk = 15 - len(self.categorie) / 2
        devolver = (("*"*int(asterisk)) + self.categorie + ("*"*int(asterisk)) + "\n")
        for i in self.ledger:
            description = ""
            amount = ""
            description = i.find("description")
            description = description + len("description  : ")
            description_str = i[description:]
            for char in i:
                if char in "0123456789.-":
                    amount += char
                amount_str = amount
            if len(description_str) < 23: 
                devolver += description_str  
                devolver += " "*(30-len(description_str)-len(amount_str))
                devolver += amount_str+ "\n"
            else:
                devolver += description_str[0:23]
                devolver += " "*(30-23-len(amount_str))
                devolver += amount_str+ "\n"
        return devolver

def create_spend_chart(categories):
    pass

food = Category("Food")
food.deposit(1000, "initial deposit")
food.withdraw(10.15, "groceries")
food.withdraw(15.89, "restaurant and more food for dessert")
print(food.get_balance())
clothing = Category("Clothing")
food.transfer(50, clothing)
clothing.withdraw(25.55)
clothing.withdraw(100)
auto = Category("Auto")
auto.deposit(1000, "initial deposit")
auto.withdraw(15)

print(food)
print(clothing)

print(create_spend_chart([food, clothing, auto]))

Answer 1

The problem is in the __str__() method, not withdraw() .

When i is an empty string, the for char in i: loop doesn't execute, so it doesn't assign amount_str . As a result, amount_str will still contain the value from the previous iteration. So any ledger entry with no cause will show with the amount from the previous iteration.

There's no need for the amount_str variable, it's the same as amount , which you correctly initialize to an empty string at the beginning of each iteration.