write data check

UI/datacheck.py

@@ -0,0 +1,12 @@
+from flask_wtf import FlaskForm
+from wtforms import StringField, PasswordField
+from wtforms.validators import InputRequired, Length, Regexp
+class LoginForm(FlaskForm):
+    username = StringField('Username', validators=[
+        InputRequired(message='Username is required.'),
+        Regexp(r'^[a-zA-Z][a-zA-Z0-9_]{0,19}$', message='Invalid username format.')
+    ])
+    password = PasswordField('Password', validators=[
+        InputRequired(message='Password is required.'),
+        Length(min=1, max=30, message='Password must be between 1 and 30 characters long.')
+    ])