Tkinter Entry变量为空，插入MySQL数据库仅生成空行问题求助

你的注册功能插入数据库时生成空数据行，核心原因及修复方案如下：

1. 核心问题：StringVar未绑定到正确窗口实例 #

每个Tkinter的Tk()对应独立的Tcl解释器，你在Signup函数中创建StringVar()时未指定所属窗口（tk3），导致变量默认绑定到第一个主窗口tk，无法关联tk3中的Entry组件，自然获取不到用户输入值。

2. 额外问题：错误的按钮命令绑定 #

forgotpassword函数中，按钮的command=PassRecovery()会立刻执行函数，而非点击按钮时触发，需去掉括号。

修正后的完整代码 #

from tkinter import *
import mysql.connector

def MainWindow():
    global tk
    tk = Tk()
    tk.geometry('300x340')
    tk.title("Login")
    label = Label(tk, text="Enter Your Credentials", fg="black")
    label.pack(side="top", pady="15px")
    label2 = Label(tk, text="Username")
    label2.pack(expand=True)
    userlog = StringVar(tk)
    userentry = Entry(tk, width=20, textvariable=userlog)
    userentry.pack(expand=True)
    label3 = Label(tk, text="Password")
    label3.pack()
    passlog = StringVar(tk)
    passentry = Entry(tk, width=20, textvariable=passlog)
    passentry.pack()
    login = Button(tk, text="Login", bg="gray")
    login.pack(pady="15px")
    forgot = Button(tk, text="Forgot password", bg="white", command=forgotpassword)
    forgot.pack()
    btn2 = Button(tk, text="Sign Up", bg="white", command=Signup)
    btn2.pack(expand=True)
    tk.mainloop()

def Withdraw():
    tk2.withdraw()
    tk.deiconify()

def forgotpassword():
    global tk2
    tk.withdraw()
    # 用Toplevel替代新Tk()，避免多实例冲突
    tk2 = Toplevel(tk)
    tk2.geometry('300x340')
    tk2.title("Forgot Password")
    lbl = Label(tk2, text="Username")
    lbl.pack(side="top", expand=True)
    userforgot = StringVar(tk2)
    usr = Entry(tk2, width=20, textvariable=userforgot)
    usr.pack(expand=True)
    lbl2 = Label(tk2, text="Phone Number")
    lbl2.pack(expand=True)
    phoneforgot = StringVar(tk2)
    phone = Entry(tk2, width=20, textvariable=phoneforgot)
    phone.pack(expand=True)
    # 去掉括号，点击按钮时才执行函数
    btn = Button(tk2, text="Forgot Password", bg="white", command=PassRecovery)
    btn.pack(expand=True)

def PassRecovery():
    #connectes to database
    #checks if datas match or not
    # if so, creates a label showing the data
    Btn = Button(tk2, text="Return to login window", command=Withdraw)
    Btn.pack(expand=True)

def Signup():
    global tk3, usersign, passsign, phonesign
    tk.withdraw()
    # 用Toplevel替代新Tk()
    tk3 = Toplevel(tk)
    tk3.geometry('300x340')
    tk3.title("Sign Up")
    lbl = Label(tk3, text="Username")
    lbl.pack(expand=True)
    # 给StringVar指定master为tk3，绑定到当前窗口
    usersign = StringVar(tk3)
    ent1 = Entry(tk3, textvariable=usersign, width=20)
    ent1.pack(expand=True)
    lbl2 = Label(tk3, text="Password")
    lbl2.pack(expand=True)
    passsign = StringVar(tk3)
    ent2 = Entry(tk3, textvariable=passsign, width=20)
    ent2.pack(expand=True)
    phonesign = StringVar(tk3)
    lbl3 = Label(tk3, text="Phone Number")
    lbl3.pack(expand=True)
    ent3 = Entry(tk3, textvariable=phonesign, width=20)
    ent3.pack(expand=True)
    btn = Button(tk3, text="Sign Up", command=InsertData)
    btn.pack(expand=True)

def InsertData():
    db = mysql.connector.connect(host="localhost", user="root", password="Balarooch1386")
    cursor = db.cursor()
    cursor.execute("use usercredentials")
    # 正确获取输入值
    username = usersign.get()
    password = passsign.get()
    phone = phonesign.get()
    cursor.execute("insert into data values (%s, %s, %s)", (username, password, phone))
    db.commit()
    labl = Label(tk3, text="Signed Up Successfully")
    labl.pack(expand=True)
    # 打印验证获取到的内容
    print(f"用户名: {username}, 密码: {password}, 手机号: {phone}")
    db.close()

MainWindow()

关键修改说明 #

• 所有StringVar创建时指定对应窗口作为master（如StringVar(tk3)），确保与Entry组件所属窗口绑定
• 用Toplevel替代多个Tk()实例，避免多解释器导致的变量绑定、事件循环冲突
• 修正按钮命令绑定，去掉不必要的lambda和括号，确保函数在点击时执行
• 在InsertData中先获取值再操作，验证输入是否正确

内容的提问来源于stack exchange，提问作者Pigeon