Tkinter更新Label文本报错：'_tkinter.tkapp'无balance_label属性

问题描述 #

执行self.balance_label['text'] = "Text updated"时触发错误：
AttributeError: '_tkinter.tkapp' object has no attribute 'balance_label'

采用分文件结构：

• file1（trade_helper.py）：GUI代码
• file2（trade_helper_support.py）：主逻辑代码

settext函数在类内部运行正常，需要实现按钮点击跨文件更新Label文本的功能。

原file1（trade_helper.py）代码 #

import sys
import tkinter as tk
import tkinter.ttk as ttk
from tkinter.constants import *
import os.path

_script = sys.argv[0]
_location = os.path.dirname(_script)

import trade_helper_support

_bgcolor = '#d9d9d9'  # X11 color: 'gray85'
_fgcolor = '#000000'  # X11 color: 'black'
_compcolor = 'gray40' # X11 color: #666666
_ana1color = '#c3c3c3' # Closest X11 color: 'gray76'
_ana2color = 'beige' # X11 color: #f5f5dc
_tabfg1 = 'black' 
_tabfg2 = 'black' 
_tabbg1 = 'grey75' 
_tabbg2 = 'grey89' 
_bgmode = 'light' 

class root:
    def __init__(self, top=None):
        '''This class configures and populates the toplevel window.
           top is the toplevel containing window.'''

        top.geometry("600x450+468+138")
        top.minsize(120, 1)
        top.maxsize(3844, 1061)
        top.resizable(1,  1)
        top.title("Trade Helper v1.0")
        top.configure(background="#d9d9d9")

        self.top = top

        self.menubar = tk.Menu(top,font="TkMenuFont",bg=_bgcolor,fg=_fgcolor)
        top.configure(menu = self.menubar)

        self.Get_balance_button = tk.Button(self.top)
        self.Get_balance_button.place(relx=0.283, rely=0.689, height=44
                , width=127)
        self.Get_balance_button.configure(activebackground="beige")
        self.Get_balance_button.configure(activeforeground="black")
        self.Get_balance_button.configure(background="#e35e8c")
        self.Get_balance_button.configure(command=trade_helper_support.get_balance)
        self.Get_balance_button.configure(compound='left')
        self.Get_balance_button.configure(disabledforeground="#a3a3a3")
        self.Get_balance_button.configure(foreground="#000000")
        self.Get_balance_button.configure(highlightbackground="#d9d9d9")
        self.Get_balance_button.configure(highlightcolor="black")
        self.Get_balance_button.configure(pady="0")
        self.Get_balance_button.configure(text='''get balance''')

        self.balance_label = tk.Label(self.top)
        self.balance_label.place(relx=0.1, rely=0.711, height=31, width=74)
        self.balance_label.configure(anchor='w')
        self.balance_label.configure(background="#ffffff")
        self.balance_label.configure(compound='left')
        self.balance_label.configure(disabledforeground="#a3a3a3")
        self.balance_label.configure(foreground="#000000")
        self.balance_label.configure(text='''Balance''')

    def settext(self):
        print('here')
        self.balance_label['text'] = "Text updated"

def start_up():
    trade_helper_support.main()

if __name__ == '__main__':
    trade_helper_support.main()

原file2（trade_helper_support.py）代码 #

import sys
import tkinter as tk
import tkinter.ttk as ttk
from tkinter.constants import *
import trade_helper

def main(*args):
    '''Main entry point for the application.'''
    global root
    root = tk.Tk()
    root.protocol( 'WM_DELETE_WINDOW' , root.destroy)
    # Creates a toplevel widget.
    global _top1, _w1
    _top1 = root
    _w1 = trade_helper.root(_top1)
    root.mainloop()

def get_balance(*args):
    print('trade_helper_support.get_balance')
    trade_helper.root.settext(root)

    for arg in args:
        print ('    another arg:', arg)
    sys.stdout.flush()

if __name__ == '__main__':
    trade_helper.start_up()

错误原因 #

在get_balance函数中，trade_helper.root.settext(root)的调用逻辑错误：

• root是Tk窗口实例，不是trade_helper.root类的实例
• settext是实例方法，必须通过trade_helper.root类的实例对象调用，而非直接调用类方法或传入Tk窗口对象

修正方案 #

方案一：使用全局保存的GUI实例 #

file2中已经全局定义了_w1（trade_helper.root的实例），直接调用其settext方法：

def get_balance(*args):
    print('trade_helper_support.get_balance')
    # 调用全局的GUI实例方法
    _w1.settext()

    for arg in args:
        print ('    another arg:', arg)
    sys.stdout.flush()

方案二：传递GUI实例到回调函数（推荐） #

1. 修改file1中按钮的command绑定，传递当前GUI实例：

# 在root类的__init__方法内修改按钮配置
self.Get_balance_button.configure(command=lambda: trade_helper_support.get_balance(self))

2. 修改file2的get_balance函数，接收实例并调用方法：

def get_balance(gui_instance, *args):
    print('trade_helper_support.get_balance')
    gui_instance.settext()

    for arg in args:
        print ('    another arg:', arg)
    sys.stdout.flush()

方案二更符合面向对象设计，避免依赖全局变量，代码耦合度更低。

内容的提问来源于stack exchange，提问作者Marc Robitaille