创建VAT计算器遇AttributeError：Label对象无get属性

问题描述 #

我正在开发一款计算产品VAT（增值税）并将数据保存至SQLite3数据库的简易计算器。计算功能正常，但点击保存按钮时无法将数据存入数据库，弹出如下错误：

line 22, in save_prod
    vat = vat_total_lbl.get()
          ^^^^^^^^^^^^^^^^^
AttributeError: 'Label' object has no attribute 'get'

相关代码 #

import tkinter as tk
from tkinter import ttk
import sqlite3

def save_prod():
    conn = sqlite3.connect('products.db')
    c = conn.cursor()

    c.execute("""CREATE TABLE IF NOT EXISTS products (
                name text,
                price real,
                vat_perc real,
                vat real,
                total real
                )""")

    name = name_entry.get()
    price = price_entry.get()
    vat_perc = vat_perc_cmb.get()
    vat = vat_total_lbl.get()
    total = total_lbl.get()

    c.execute("""INSERT INTO products (name, price, vat_perc, vat, total)
            VALUES (?,?,?,?,?)""", (name, price, vat_perc, vat, total))

    conn.commit()
    conn.close()
    status_lbl.config(text="Product saved successfully")

def vat():
    try:
        price = float(price_entry.get())
        vat_perc = float(vat_perc_cmb.get())
        vat = price * vat_perc / 100
        total = price + vat
        vat_total_lbl.config(text="VAT Amount: {:.2f}".format(vat))
        total_lbl.config(text="Total Price: {:.2f}".format(total))
        #in case non numeric values entered
    except ValueError:
        vat_total_lbl.config(text="Invalid input!")
        total_lbl.config(text="Invalid input!")

window = tk.Tk()
window.title("Create a New Product")

prod_create_label = tk.Label(text="Create a New Product")
prod_create_label.grid(row=0, column=2)

name_lbl = tk.Label(text="Item Name: ")
name_lbl.grid(row=2, column=0)

name_entry = tk.Entry()
name_entry.grid(row=3, column=0)

price_lbl = tk.Label(text="Item Price: ")
price_lbl.grid(row=2, column=1)

price_entry = tk.Entry()
price_entry.grid(row=3, column=1)

vat_perc_lbl = tk.Label(text="Item's VAT Percentage: ")
vat_perc_lbl.grid(row=2, column=2)

course=["23", "13.5", "9"]
vat_perc_cmb = ttk.Combobox(window, value=course, width=10)
vat_perc_cmb.grid(row=3, column=2)
vat_perc_cmb.current(2)

cal_vat_btn = tk.Button(text="Calculate VAT and Total Price", command=vat)
cal_vat_btn.grid(row=3, column=3)

vat_lbl = tk.Label(text="Item's VAT total: ")
vat_lbl.grid(row=4, column=0)

vat_total_lbl = tk.Label()
vat_total_lbl.grid(row=5, column=0)

total = tk.Label(text="Item's total price: ")
total.grid(row=4, column=1)

total_lbl = tk.Label()
total_lbl.grid(row=5, column=1)

save_btn = tk.Button(text="Save Product", command=save_prod)
save_btn.grid(row=6, column=0)

status_lbl = tk.Label(text="")
status_lbl.grid(row=6, column=1)

window.mainloop()

问题根源 #

vat_total_lbl和total_lbl是Tkinter的Label组件，Label没有get()方法，你错误地沿用了Entry组件的取值方式，导致抛出AttributeError。

修复方案 #

方案1：重新计算VAT和总价（推荐） #

无需从Label提取数据，保存时直接基于输入的价格和税率重新计算，避免依赖Label的文本内容，同时增加输入验证：

def save_prod():
    conn = sqlite3.connect('products.db')
    c = conn.cursor()

    try:
        name = name_entry.get().strip()
        if not name:
            status_lbl.config(text="Item name cannot be empty!")
            return
        
        price = float(price_entry.get())
        if price <= 0:
            status_lbl.config(text="Price must be a positive number!")
            return
            
        vat_perc = float(vat_perc_cmb.get())
        # 重新计算vat和total
        vat = price * vat_perc / 100
        total = price + vat

        c.execute("""INSERT INTO products (name, price, vat_perc, vat, total)
                VALUES (?,?,?,?,?)""", (name, price, vat_perc, vat, total))

        conn.commit()
        status_lbl.config(text="Product saved successfully")
    except ValueError:
        status_lbl.config(text="Invalid input! Check your price value.")
    finally:
        conn.close()

方案2：从Label文本中提取数值 #

如果一定要从Label取值，需要先获取Label的text属性，再提取其中的数值部分：

def save_prod():
    conn = sqlite3.connect('products.db')
    c = conn.cursor()

    try:
        name = name_entry.get().strip()
        if not name:
            status_lbl.config(text="Item name cannot be empty!")
            return
        
        price = float(price_entry.get())
        vat_perc = float(vat_perc_cmb.get())
        
        # 提取Label中的数值
        vat_text = vat_total_lbl.cget("text")
        if "Invalid input" in vat_text:
            status_lbl.config(text="Please calculate VAT first!")
            return
        vat = float(vat_text.split(": ")[1])
        
        total_text = total_lbl.cget("text")
        total = float(total_text.split(": ")[1])

        c.execute("""INSERT INTO products (name, price, vat_perc, vat, total)
                VALUES (?,?,?,?,?)""", (name, price, vat_perc, vat, total))

        conn.commit()
        status_lbl.config(text="Product saved successfully")
    except (ValueError, IndexError):
        status_lbl.config(text="Invalid data! Ensure you've calculated VAT correctly.")
    finally:
        conn.close()

额外优化建议 #

• 将CREATE TABLE逻辑移到程序初始化部分，无需每次保存时执行，提升效率
• 增加输入验证，比如检查名称是否为空、价格是否为正数
• 可以使用全局变量或类属性存储计算后的vat和total，避免重复计算或文本解析

内容的提问来源于stack exchange，提问作者Kate Murphy