Python: AttributeError: 'str' object has no attribute when calling a method inside for loop

Question

当我尝试使用由 for 循环生成的名称访问 class 实例时，我得到

"AttributeError: 'str' object has no attribute".

我是 Python 的新手，请原谅 "Not the best practice"。感谢任何帮助

class Csv:
    def __init__(self, invoicenum, customer, invoicedate, duedate, description, amount, productservice, invoiceclass):
        self.invoicenum = invoicenum
        self.customer = customer
        self.invoicedate = invoicedate
        self.duedate = duedate
        self.description = description
        self.amount = amount
        self.productservice = productservice
        self.invoiceclass = invoiceclass
        self.line = '{},{},{},{},{},{},{},{}\n'.format(invoicenum, customer, invoicedate,
                                                       duedate, description, amount, productservice, invoiceclass)

    def wite_to_db(self):
        mydb = mysql.connector.connect(host="localhost", user="root",
                                       passwd="passwd", database="invoice")
        mycursor = mydb.cursor()
        sql = "insert into invoice " "(Invoice_no, Customer, Invoice_Date, Due_date, Description, Amount, Product_service, Class)" "VALUES (%s,%s,%s,%s,%s,%s,%s,%s)"
        val = (self.invoicenum, self.customer, self.invoicedate, self.duedate,
               self.description, self.amount, self.productservice, self.invoiceclass)
        mycursor.execute(sql, val)
        mydb.commit()


x0 = Csv("1355", "Test1 User", "2020-05-03", "2020-12-31", 7095, 300, "Tithe", "General Fund")
x1 = Csv("1124", "Test2 User", "2020-05-03", "2020-12-31", 7095, 300, "Tithe", "General Fund")
x2 = Csv("14432", "Test3 User", "2020-05-03", "2020-12-31", 7095, 300, "Tithe", "General Fund")
x3 = Csv("1312", "Test4 User", "2020-05-03", "2020-12-31", 7095, 300, "Tithe", "General Fund")


line_range = range(4)

for line in line_range:
    line_instance = 'x' + str(line)
    print(line_instance)
    line_instance.write_to_db()

Answer 1

line_instance = 'x' + str(line)
print(line_instance)
line_instance.write_to_db()

这是错误的。字符串没有 write_to_db 方法。您在 Csv class 中定义了此方法（或者更确切地说是名称非常相似的 wite_to_db...），但 line_instance 显然是此处的字符串，而不是 [=14 的实例=] class。您可能想要做的是：

for line_instance in (x0, x1, x2, x3):
    line_instance.write_to_db()

Answer 2

你所做的是当你创建 line_instance 变量时，你把它变成了一个字符串，然后几行之后你基本上尝试运行你的 Csv 中的函数 class - write_to_db 在一个字符串上。这就是错误发生的原因。

我可以推荐的做法如下：

x0 = Csv(...
x1 = Csv(...
x2 = Csv(...
x3 = Csv(...

x_list = [x0, x1, x2, x3]

for x in x_list:
    x.write_to_db()

旁注，您在 Csv class

中的“wite_to_db”函数定义中有错字

Answer 3

line_instance 是一个 str。 str 没有调用 write_to_db

的函数

Answer 4

我将 class 个实例分配给了一个列表，并且能够为遍历它的实例调用该方法。你们都很棒。

Python: AttributeError: 'str' object has no attribute when calling a method inside for loop

Python: AttributeError: 'str' object has no attribute when calling a method inside for loop

python

attributeerror

旁注，您在 Csv class