CustomTkinter登录GUI开发报错：NameError: name 'username_entry' is not defined

数据老陈

2026-8-9

解决CustomTkinter登录GUI调用脚本时的NameError问题

问题场景

使用CustomTkinter开发登录GUI，主窗口包含Login和Exit按钮，点击Login按钮调用login.py打开登录界面。单独运行login.py一切正常，但从主脚本触发调用时出现如下错误：

Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Users\denis\AppData\Local\Programs\Python\Python311\Lib\tkinter\__init__.py", line 1948, in __call__
    return self.func(*args)
           ^^^^^^^^^^^^^^^^
  File "D:\test\venv\Lib\site-packages\customtkinter\windows\widgets\ctk_button.py", line 527, in _clicked
    self._command()
  File "<string>", line 21, in login
NameError: name 'username_entry' is not defined

主脚本代码

import tkinter
import customtkinter


customtkinter.set_appearance_mode("System") 
customtkinter.set_default_color_theme("dark-blue")  

app = customtkinter.CTk()  # create CTk window like you do with the Tk window
app.title("Menu")
app.geometry("240x240")
app.config(bg="#242320")

def button_function():
    exec(open('D:\\test\\login.py').read())

def Close():
    app.destroy()

font1=('Arial', 15, 'bold')

button = customtkinter.CTkButton(master=app, text="Login", font=font1, command=button_function)
button.place(relx=0.5, rely=0.4, anchor=tkinter.CENTER)
button = customtkinter.CTkButton(master=app, text="Exit", font=font1, command=Close)
button.place(relx=0.5, rely=0.6, anchor=tkinter.CENTER)


app.mainloop()

登录脚本login.py代码

import customtkinter
from tkinter import *
from tkinter import messagebox


app = customtkinter.CTk()
app.title("Login")
app.geometry("350x200")
app.config(bg="#242320")

font1=('Arial', 15, 'bold')

username="hello"
password="123"
trials=0

def login():
    global username
    global password
    global trials
    written_username = username_entry.get()
    written_password = password_entry.get()
    if(written_username == '' or written_password==''):
        messagebox.showwarning(title="Error", message="Enter your username and password.")
    elif(written_username==username and written_password==password):
        new_window=Toplevel(app)
        new_window.geometry("350x200")
        new_window.config(bg="#242320")
        welcome_label=customtkinter.CTkLabel(new_window, text="Welcome...", font=font1, text_color="#FFFFFF")
        welcome_label.place(x=100, y=100)
    elif((written_username != username or written_password != password) and trials<3):
        messagebox.showerror(title="Error", message="Your username or password are not correct.")
        trials=trials + 1
        if (trials != 3):
            trials_label = customtkinter.CTkLabel(app, text=f"You have {3-trials} trials", font=font1, text_color="#FFFFFF")
            trials_label.place(x=100, y=160)
        if(trials==3):
            login_button.destroy()
            locked_label = customtkinter.CTkLabel(app, text="Your account is locked.", font=font1, text_color="#FFFFFF")
            locked_label.place(x=100, y=160)

username_label=customtkinter.CTkLabel(app, text="Username: ",font=font1, text_color="#FFFFFF")
username_label.place(x=10, y=25)

password_label=customtkinter.CTkLabel(app, text="Password: ",font=font1, text_color="#FFFFFF")
password_label.place(x=10, y=75)

username_entry=customtkinter.CTkEntry(app,fg_color="#FFFFFF", font=font1, text_color="#000000", border_color="#FFFFFF", width= 200, height= 1)
username_entry.place(x=100, y=25)

password_entry=customtkinter.CTkEntry(app,fg_color="#FFFFFF", font=font1, text_color="#000000", border_color="#FFFFFF", show="*",  width= 200, height= 1)
password_entry.place(x=100, y=75)

login_button=customtkinter.CTkButton(app, command=login,  text="Login", font=font1, text_color="#FFFFFF", fg_color="#1f538d", hover_color="#14375e", width=50)
login_button.place(x=165, y=120)




app.mainloop()

问题原因与解决方法

原因

使用exec(open('login.py').read())执行脚本时，login.py中的username_entry等变量处于局部作用域，login()函数无法直接访问这些未声明为全局的变量。
主脚本和login.py都创建了名为app的CTk实例，导致上下文混乱，进一步加剧了作用域问题。

解决步骤

1. 重构login.py，封装登录窗口逻辑

将登录窗口的创建逻辑封装为函数，通过nonlocal声明函数需要访问的外层变量，确保作用域正确：

import customtkinter
from tkinter import messagebox

def show_login_window():
    login_app = customtkinter.CTk()
    login_app.title("Login")
    login_app.geometry("350x200")
    login_app.config(bg="#242320")

    font1=('Arial', 15, 'bold')

    username="hello"
    password="123"
    trials=0

    def login():
        nonlocal username, password, trials, login_app, username_entry, password_entry, login_button
        written_username = username_entry.get()
        written_password = password_entry.get()
        if written_username == '' or written_password=='':
            messagebox.showwarning(title="Error", message="Enter your username and password.")
        elif written_username == username and written_password == password:
            new_window = customtkinter.CTkToplevel(login_app)
            new_window.geometry("350x200")
            new_window.config(bg="#242320")
            welcome_label = customtkinter.CTkLabel(new_window, text="Welcome...", font=font1, text_color="#FFFFFF")
            welcome_label.place(x=100, y=100)
        elif (written_username != username or written_password != password) and trials < 3:
            messagebox.showerror(title="Error", message="Your username or password are not correct.")
            trials += 1
            if trials != 3:
                trials_label = customtkinter.CTkLabel(login_app, text=f"You have {3-trials} trials", font=font1, text_color="#FFFFFF")
                trials_label.place(x=100, y=160)
            if trials == 3:
                login_button.destroy()
                locked_label = customtkinter.CTkLabel(login_app, text="Your account is locked.", font=font1, text_color="#FFFFFF")
                locked_label.place(x=100, y=160)

    username_label = customtkinter.CTkLabel(login_app, text="Username: ",font=font1, text_color="#FFFFFF")
    username_label.place(x=10, y=25)

    password_label = customtkinter.CTkLabel(login_app, text="Password: ",font=font1, text_color="#FFFFFF")
    password_label.place(x=10, y=75)

    username_entry = customtkinter.CTkEntry(login_app,fg_color="#FFFFFF", font=font1, text_color="#000000", border_color="#FFFFFF", width=200, height=25)
    username_entry.place(x=100, y=25)

    password_entry = customtkinter.CTkEntry(login_app,fg_color="#FFFFFF", font=font1, text_color="#000000", border_color="#FFFFFF", show="*", width=200, height=25)
    password_entry.place(x=100, y=75)

    login_button = customtkinter.CTkButton(login_app, command=login, text="Login", font=font1, text_color="#FFFFFF", fg_color="#1f538d", hover_color="#14375e", width=50)
    login_button.place(x=165, y=120)

    login_app.mainloop()

# 单独运行时启动窗口
if __name__ == "__main__":
    show_login_window()

2. 修改主脚本，通过导入模块调用函数

替换exec方式，改为导入login.py并调用封装好的函数：

import tkinter
import customtkinter
import login

customtkinter.set_appearance_mode("System") 
customtkinter.set_default_color_theme("dark-blue")  

app = customtkinter.CTk()
app.title("Menu")
app.geometry("240x240")
app.config(bg="#242320")

def button_function():
    login.show_login_window()

def Close():
    app.destroy()

font1=('Arial', 15, 'bold')

button = customtkinter.CTkButton(master=app, text="Login", font=font1, command=button_function)
button.place(relx=0.5, rely=0.4, anchor=tkinter.CENTER)
button = customtkinter.CTkButton(master=app, text="Exit", font=font1, command=Close)
button.place(relx=0.5, rely=0.6, anchor=tkinter.CENTER)

app.mainloop()

关键改动说明

用函数封装登录窗口逻辑，通过nonlocal确保内部函数能访问外层变量，解决作用域问题。
使用模块导入替代exec，避免脚本执行时的上下文混乱。
替换Toplevel为customtkinter.CTkToplevel，保持CustomTkinter组件风格一致。
调整输入框height参数为25，修复原代码中输入框显示异常的问题。

内容的提问来源于stack exchange，提问作者Alpha

CustomTkinter登录GUI开发报错：NameError: name 'username_entry' is not defined

问题场景 #

主脚本代码 #

登录脚本login.py代码 #

问题原因与解决方法 #

原因 #

解决步骤 #