auto save

my_app.py

 import tkinter
+from tkinter import messagebox
+
+with open("user.txt","r", encoding="utf-8") as f:
+    info = f.read()
+    users = json
+def login_to_reg():
+    app_login.root.destroy()
+    global app_reg
+    app_reg = My_register()
+    app_reg.show()
+
+def reg_to_login():
+    app_login.root.destroy()
+    global app_login
+    app_reg = My_login()
+    app_reg.show()
+
+def register():
+    name,password1,password2 = app_reg.get_input()
+    if name =="" or password1=="" or password2=="":
+        messagebox.showwarning("警告","请填写完整的注册资料")
+    elif name in users:
+        messagebox.showwarning("错误", "用户名已经存在!")
+
 
 def login_to_reg():    # 登录界面转注册界面
     pass