python - Flask_form : CSRF Token do not match -

i'm using flask_form in flask application , have being stucked hours 'csrf token not match'.

<form method="post" action="{{ url_for('auth.login') }}" role="form">     {{ form.hidden_tag() }}     {{ wtf.form_errors(form, hiddens="only") }}     {{ wtf.form_field(form.email)}}     {{ wtf.form_field(form.password)}}     <p><button type="submit">login</button></p> </form> 

views.py

@auth.route('/login', methods=['get', 'post']) def login():      form = loginform()     if form.validate_on_submit():          print('login form received on server , valid')         # check whether user exists in database , whether         # password entered matches password in database         user = user.query.filter_by(email=form.email.data).first()         if user not none , user.verify_password(form.password.data) , check_password_hash(user.pwd, form.password.data):             # log employee in             login_user(user) #,remember=true)              # redirect home page after login             return redirect(url_for('grapher.upload'))          # when login details incorrect         else:             flash('invalid email or password.', 'info')      # load login template     return render_template('auth/login.html', form=form, title='login') 

form

class loginform(flaskform):     email = stringfield('email', validators=[datarequired(), email(),    length(min=1,max=254, message='the maximum length of filed 254 characters')])     password = passwordfield('password', validators=[datarequired(), length(max=20, message='password maximium length 20 characters.')]) 

why error?

you need add csrf input field in form said in docs:

<form method="post">   {{ form.csrf_token }} </form> 

every wtforms validation checks availability of token in post request data unless explicitly disabled.