2018-01-02T17:20:33Z

The Flask Mega-Tutorial Part V: User Logins

This is the fifth installment of the Flask Mega-Tutorial series, in which I'm going to tell you how to create a user login subsystem.

For your reference, below is a list of the articles in this series.

In Chapter 3 you learned how to create the user login form, and in Chapter 4 you learned how to work with a database. This chapter will teach you how to combine the topics from those two chapters to create a simple user login system.

The GitHub links for this chapter are: Browse, Zip, Diff.

Password Hashing

In Chapter 4 the user model was given a password_hash field, that so far is unused. The purpose of this field is to hold a hash of the user password, which will be used to verify the password entered by the user during the log in process. Password hashing is a complicated topic that should be left to security experts, but there are several easy to use libraries that implement all that logic in a way that is simple to be invoked from an application.

One of the packages that implement password hashing is Werkzeug, which you may have seen referenced in the output of pip when you install Flask, since it is one of its core dependencies. Since it is a dependency, Werkzeug is already installed in your virtual environment. The following Python shell session demonstrates how to hash a password:

>>> from werkzeug.security import generate_password_hash
>>> hash = generate_password_hash('foobar')
>>> hash
'pbkdf2:sha256:50000$vT9fkZM8$04dfa35c6476acf7e788a1b5b3c35e217c78dc04539d295f011f01f18cd2'

In this example, the password foobar is transformed into a long encoded string through a series of cryptographic operations that have no known reverse operation, which means that a person that obtains the hashed password will be unable to use it to obtain the original password. As an additional measure, if you hash the same password multiple times, you will get different results, so this makes it impossible to identify if two users have the same password by looking at their hashes.

The verification process is done with a second function from Werkzeug, as follows:

>>> from werkzeug.security import check_password_hash
>>> check_password_hash(hash, 'foobar')
True
>>> check_password_hash(hash, 'barfoo')
False

The verification function takes a password hash that was previously generated, and a password entered by the user at the time of log in. The function returns True if the password provided by the user matches the hash, or False otherwise.

The whole password hashing logic can be implemented as two new methods in the user model:

app/models.py: Password hashing and verification

from werkzeug.security import generate_password_hash, check_password_hash

# ...

class User(db.Model):
    # ...

    def set_password(self, password):
        self.password_hash = generate_password_hash(password)

    def check_password(self, password):
        return check_password_hash(self.password_hash, password)

With these two methods in place, a user object is now able to do secure password verification, without the need to ever store original passwords. Here is an example usage of these new methods:

>>> u = User(username='susan', email='susan@example.com')
>>> u.set_password('mypassword')
>>> u.check_password('anotherpassword')
False
>>> u.check_password('mypassword')
True

Introduction to Flask-Login

In this chapter I'm going to introduce you to a very popular Flask extension called Flask-Login. This extension manages the user logged-in state, so that for example users can log in to the application and then navigate to different pages while the application "remembers" that the user is logged in. It also provides the "remember me" functionality that allows users to remain logged in even after closing the browser window. To be ready for this chapter, you can start by installing Flask-Login in your virtual environment:

(venv) $ pip install flask-login

As with other extensions, Flask-Login needs to be created and initialized right after the application instance in app/__init__.py. This is how this extension is initialized:

app/__init__.py: Flask-Login initialization

# ...
from flask_login import LoginManager

app = Flask(__name__)
# ...
login = LoginManager(app)

# ...

Preparing The User Model for Flask-Login

The Flask-Login extension works with the application's user model, and expects certain properties and methods to be implemented in it. This approach is nice, because as long as these required items are added to the model, Flask-Login does not have any other requirements, so for example, it can work with user models that are based on any database system.

The four required items are listed below:

  • is_authenticated: a property that is True if the user has valid credentials or False otherwise.
  • is_active: a property that is True if the user's account is active or False otherwise.
  • is_anonymous: a property that is False for regular users, and True for a special, anonymous user.
  • get_id(): a method that returns a unique identifier for the user as a string (unicode, if using Python 2).

I can implement these four easily, but since the implementations are fairly generic, Flask-Login provides a mixin class called UserMixin that includes generic implementations that are appropriate for most user model classes. Here is how the mixin class is added to the model:

app/models.py: Flask-Login user mixin class

# ...
from flask_login import UserMixin

class User(UserMixin, db.Model):
    # ...

User Loader Function

Flask-Login keeps track of the logged in user by storing its unique identifier in Flask's user session, a storage space assigned to each user who connects to the application. Each time the logged-in user navigates to a new page, Flask-Login retrieves the ID of the user from the session, and then loads that user into memory.

Because Flask-Login knows nothing about databases, it needs the application's help in loading a user. For that reason, the extension expects that the application will configure a user loader function, that can be called to load a user given the ID. This function can be added in the app/models.py module:

app/models.py: Flask-Login user loader function

from app import login
# ...

@login.user_loader
def load_user(id):
    return User.query.get(int(id))

The user loader is registered with Flask-Login with the @login.user_loader decorator. The id that Flask-Login passes to the function as an argument is going to be a string, so databases that use numeric IDs need to convert the string to integer as you see above.

Logging Users In

Let's revisit the login view function, which as you recall, implemented a fake login that just issued a flash() message. Now that the application has access to a user database and knows how to generate and verify password hashes, this view function can be completed.

app/routes.py: Login view function logic

# ...
from flask_login import current_user, login_user
from app.models import User

# ...

@app.route('/login', methods=['GET', 'POST'])
def login():
    if current_user.is_authenticated:
        return redirect(url_for('index'))
    form = LoginForm()
    if form.validate_on_submit():
        user = User.query.filter_by(username=form.username.data).first()
        if user is None or not user.check_password(form.password.data):
            flash('Invalid username or password')
            return redirect(url_for('login'))
        login_user(user, remember=form.remember_me.data)
        return redirect(url_for('index'))
    return render_template('login.html', title='Sign In', form=form)

The top two lines in the login() function deal with a weird situation. Imagine you have a user that is logged in, and the user navigates to the /login URL of your application. Clearly that is a mistake, so I want to not allow that. The current_user variable comes from Flask-Login and can be used at any time during the handling to obtain the user object that represents the client of the request. The value of this variable can be a user object from the database (which Flask-Login reads through the user loader callback I provided above), or a special anonymous user object if the user did not log in yet. Remember those properties that Flask-Login required in the user object? One of those was is_authenticated, which comes in handy to check if the user is logged in or not. When the user is already logged in, I just redirect to the index page.

In place of the flash() call that I used earlier, now I can log the user in for real. The first step is to load the user from the database. The username came with the form submission, so I can query the database with that to find the user. For this purpose I'm using the filter_by() method of the SQLAlchemy query object. The result of filter_by() is a query that only includes the objects that have a matching username. Since I know there is only going to be one or zero results, I complete the query by calling first(), which will return the user object if it exists, or None if it does not. In Chapter 4 you have seen that when you call the all() method in a query, the query executes and you get a list of all the results that match that query. The first() method is another commonly used way to execute a query, when you only need to have one result.

If I got a match for the username that was provided, I can next check if the password that also came with the form is valid. This is done by invoking the check_password() method I defined above. This will take the password hash stored with the user and determine if the password entered in the form matches the hash or not. So now I have two possible error conditions: the username can be invalid, or the password can be incorrect for the user. In either of those cases, I flash an message, and redirect back to the login prompt so that the user can try again.

If the username and password are both correct, then I call the login_user() function, which comes from Flask-Login. This function will register the user as logged in, so that means that any future pages the user navigates to will have the current_user variable set to that user.

To complete the login process, I just redirect the newly logged-in user to the index page.

Logging Users Out

I know I will also need to offer users the option to log out of the application. This can be done with Flask-Login's logout_user() function. Here is the logout view function:

app/routes.py: Logout view function

# ...
from flask_login import logout_user

# ...

@app.route('/logout')
def logout():
    logout_user()
    return redirect(url_for('index'))

To expose this link to users, I can make the Login link in the navigation bar automatically switch to a Logout link after the user logs in. This can be done with a conditional in the base.html template:

app/templates/base.html: Conditional login and logout links

    <div>
        Microblog:
        <a href="{{ url_for('index') }}">Home</a>
        {% if current_user.is_anonymous %}
        <a href="{{ url_for('login') }}">Login</a>
        {% else %}
        <a href="{{ url_for('logout') }}">Logout</a>
        {% endif %}
    </div>

The is_anonymous property is one of the attributes that Flask-Login adds to user objects through the UserMixin class. The current_user.is_anonymous expression is going to be True only when the user is not logged in.

Requiring Users To Login

Flask-Login provides a very useful feature that forces users to log in before they can view certain pages of the application. If a user who is not logged in tries to view a protected page, Flask-Login will automatically redirect the user to the login form, and only redirect back to the page the user wanted to view after the login process is complete.

For this feature to be implemented, Flask-Login needs to know what is the view function that handles logins. This can be added in app/__init__.py:

# ...
login = LoginManager(app)
login.login_view = 'login'

The 'login' value above is the function (or endpoint) name for the login view. In other words, the name you would use in a url_for() call to get the URL.

The way Flask-Login protects a view function against anonymous users is with a decorator called @login_required. When you add this decorator to a view function below the @app.route decorators from Flask, the function becomes protected and will not allow access to users that are not authenticated. Here is how the decorator can be applied to the index view function of the application:

app/routes.py: @login\_required decorator

from flask_login import login_required

@app.route('/')
@app.route('/index')
@login_required
def index():
    # ...

What remains is to implement the redirect back from the successful login to the page the user wanted to access. When a user that is not logged in accesses a view function protected with the @login_required decorator, the decorator is going to redirect to the login page, but it is going to include some extra information in this redirect so that the application can then return to the first page. If the user navigates to /index, for example, the @login_required decorator will intercept the request and respond with a redirect to /login, but it will add a query string argument to this URL, making the complete redirect URL /login?next=/index. The next query string argument is set to the original URL, so the application can use that to redirect back after login.

Here is a snippet of code that shows how to read and process the next query string argument:

app/routes.py: Redirect to "next" page

from flask import request
from werkzeug.urls import url_parse

@app.route('/login', methods=['GET', 'POST'])
def login():
    # ...
    if form.validate_on_submit():
        user = User.query.filter_by(username=form.username.data).first()
        if user is None or not user.check_password(form.password.data):
            flash('Invalid username or password')
            return redirect(url_for('login'))
        login_user(user, remember=form.remember_me.data)
        next_page = request.args.get('next')
        if not next_page or url_parse(next_page).netloc != '':
            next_page = url_for('index')
        return redirect(next_page)
    # ...

Right after the user is logged in by calling Flask-Login's login_user() function, the value of the next query string argument is obtained. Flask provides a request variable that contains all the information that the client sent with the request. In particular, the request.args attribute exposes the contents of the query string in a friendly dictionary format. There are actually three possible cases that need to be considered to determine where to redirect after a successful login:

  • If the login URL does not have a next argument, then the user is redirected to the index page.
  • If the login URL includes a next argument that is set to a relative path (or in other words, a URL without the domain portion), then the user is redirected to that URL.
  • If the login URL includes a next argument that is set to a full URL that includes a domain name, then the user is redirected to the index page.

The first and second cases are self-explanatory. The third case is in place to make the application more secure. An attacker could insert a URL to a malicious site in the next argument, so the application only redirects when the URL is relative, which ensures that the redirect stays within the same site as the application. To determine if the URL is relative or absolute, I parse it with Werkzeug's url_parse() function and then check if the netloc component is set or not.

Showing The Logged In User in Templates

Do you recall that way back in Chapter 2 I created a fake user to help me design the home page of the application before the user subsystem was in place? Well, the application has real users now, so I can now remove the fake user and start working with real users. Instead of the fake user I can use Flask-Login's current_user in the template:

app/templates/index.html: Pass current user to template

{% extends "base.html" %}

{% block content %}
    <h1>Hi, {{ current_user.username }}!</h1>
    {% for post in posts %}
    <div><p>{{ post.author.username }} says: <b>{{ post.body }}</b></p></div>
    {% endfor %}
{% endblock %}

And I can remove the user template argument in the view function:

app/routes.py: Do not pass user to template anymore

@app.route('/')
@app.route('/index')
@login_required
def index():
    # ...
    return render_template("index.html", title='Home Page', posts=posts)

This is a good time to test how the login and logout functionality works. Since there is still no user registration, the only way to add a user to the database is to do it via the Python shell, so run flask shell and enter the following commands to register a user:

>>> u = User(username='susan', email='susan@example.com')
>>> u.set_password('cat')
>>> db.session.add(u)
>>> db.session.commit()

If you start the application and go to the application's / or /index URLs, you will be immediately redirected to the login page, and after you log in using the credentials of the user that you added to your database, you will be returned to the original page, in which you will see a personalized greeting.

User Registration

The last piece of functionality that I'm going to build in this chapter is a registration form, so that users can register themselves through a web form. Let's begin by creating the web form class in app/forms.py:

app/forms.py: User registration form

from flask_wtf import FlaskForm
from wtforms import StringField, PasswordField, BooleanField, SubmitField
from wtforms.validators import ValidationError, DataRequired, Email, EqualTo
from app.models import User

# ...

class RegistrationForm(FlaskForm):
    username = StringField('Username', validators=[DataRequired()])
    email = StringField('Email', validators=[DataRequired(), Email()])
    password = PasswordField('Password', validators=[DataRequired()])
    password2 = PasswordField(
        'Repeat Password', validators=[DataRequired(), EqualTo('password')])
    submit = SubmitField('Register')

    def validate_username(self, username):
        user = User.query.filter_by(username=username.data).first()
        if user is not None:
            raise ValidationError('Please use a different username.')

    def validate_email(self, email):
        user = User.query.filter_by(email=email.data).first()
        if user is not None:
            raise ValidationError('Please use a different email address.')

There are a couple of interesting things in this new form related to validation. First, for the email field I've added a second validator after DataRequired, called Email. This is another stock validator that comes with WTForms that will ensure that what the user types in this field matches the structure of an email address.

The Email() validator from WTForms requires an external dependency to be installed:

(venv) $ pip install email-validator

Since this is a registration form, it is customary to ask the user to type the password two times to reduce the risk of a typo. For that reason I have password and password2 fields. The second password field uses yet another stock validator called EqualTo, which will make sure that its value is identical to the one for the first password field.

When you add any methods that match the pattern validate_<field_name>, WTForms takes those as custom validators and invokes them in addition to the stock validators. I have added two of those methods to this class for the username and email fields. In this case I want to make sure that the username and email address entered by the user are not already in the database, so these two methods issue database queries expecting there will be no results. In the event a result exists, a validation error is triggered by raising an exception of type ValidationError. The message included as the argument in the exception will be the message that will be displayed next to the field for the user to see.

To display this form on a web page, I need to have an HTML template, which I'm going to store in file app/templates/register.html. This template is constructed similarly to the one for the login form:

app/templates/register.html: Registration template

{% extends "base.html" %}

{% block content %}
    <h1>Register</h1>
    <form action="" method="post">
        {{ form.hidden_tag() }}
        <p>
            {{ form.username.label }}<br>
            {{ form.username(size=32) }}<br>
            {% for error in form.username.errors %}
            <span style="color: red;">[{{ error }}]</span>
            {% endfor %}
        </p>
        <p>
            {{ form.email.label }}<br>
            {{ form.email(size=64) }}<br>
            {% for error in form.email.errors %}
            <span style="color: red;">[{{ error }}]</span>
            {% endfor %}
        </p>
        <p>
            {{ form.password.label }}<br>
            {{ form.password(size=32) }}<br>
            {% for error in form.password.errors %}
            <span style="color: red;">[{{ error }}]</span>
            {% endfor %}
        </p>
        <p>
            {{ form.password2.label }}<br>
            {{ form.password2(size=32) }}<br>
            {% for error in form.password2.errors %}
            <span style="color: red;">[{{ error }}]</span>
            {% endfor %}
        </p>
        <p>{{ form.submit() }}</p>
    </form>
{% endblock %}

The login form template needs a link that sends new users to the registration form, right below the form:

app/templates/login.html: Link to registration page

    <p>New User? <a href="{{ url_for('register') }}">Click to Register!</a></p>

And finally, I need to write the view function that is going to handle user registrations in app/routes.py:

app/routes.py: User registration view function

from app import db
from app.forms import RegistrationForm

# ...

@app.route('/register', methods=['GET', 'POST'])
def register():
    if current_user.is_authenticated:
        return redirect(url_for('index'))
    form = RegistrationForm()
    if form.validate_on_submit():
        user = User(username=form.username.data, email=form.email.data)
        user.set_password(form.password.data)
        db.session.add(user)
        db.session.commit()
        flash('Congratulations, you are now a registered user!')
        return redirect(url_for('login'))
    return render_template('register.html', title='Register', form=form)

And this view function should also be mostly self-explanatory. I first make sure the user that invokes this route is not logged in. The form is handled in the same way as the one for logging in. The logic that is done inside the if validate_on_submit() conditional creates a new user with the username, email and password provided, writes it to the database, and then redirects to the login prompt so that the user can log in.

Registration Form

With these changes, users should be able to create accounts on this application, and log in and out. Make sure you try all the validation features I've added in the registration form to better understand how they work. I am going to revisit the user authentication subsystem in a future chapter to add additional functionality such as to allow the user to reset the password if forgotten. But for now, this is enough to continue building other areas of the application.

578 comments

  • #276 shi said 2019-05-11T05:59:36Z

    This is a GREAT tutorial series and I had followed it all the way here. However I am having an issue about my Registration process: after I fill in the form with valid inputs and click the submit button, the page says "Not Found The requested URL was not found on the server. If you entered the URL manually please check your spelling and try again." And in the address bar, it shows something like this: "http://localhost:5000/%22%20method=%22post?csrf_token=IjNhYThlNWExMzIyMzllYTg4YmI0YmM0OWQ1NzlkYzI0MThlYmIxNzgi.XNZi7w.d7MWIkclladVVH9rqFxSmqZ_9JM&username=a&email=a%40gmail.com&password=a&password2=a&submit=Register"

    what are the possible reasons for this error? And more importantly, how can I debug for issues like this? Thanks!

  • #277 Miguel Grinberg said 2019-05-11T21:08:46Z

    @shi: check the element in your template file, you very likely have a typo there.

  • #278 Igor said 2019-05-13T22:19:06Z

    I have a question. The line "form = RegistrationForm()", it is automagically populated with fields which client populated. Is this some feature of Flask Forms?

    Thank you.

    Borota Igor

  • #279 Karl Wraith said 2019-05-14T03:58:58Z

    Hi Miguel, I have just completed password hashing and have this error 'AttributeError: 'User' object has no attribute 'set_password' when I run u.set_password('mypassword') under Flask Shell. I have checked my models.py and it appears OK. Can you help me?

    models.py from datetime import datetime from werkzeug.security import generate_password_hash, check_password_hash from app import db

    class User(db.Model): id = db.Column(db.Integer, primary_key=True) username = db.Column(db.String(64), index=True, unique=True) email = db.Column(db.String(120), index=True, unique=True) password_hash = db.Column(db.String(128)) posts = db.relationship('Post', backref='author', lazy='dynamic')

    def __repr__(self): return '<User {}>'.format(self.username) def set_password(self, password): self.password_hash = generate_password_hash(password) def check_password(self, password): return check_password_hash(self.password_hash, password)

    class Post(db.Model): id = db.Column(db.Integer, primary_key=True) body = db.Column(db.String(140)) timestamp = db.Column(db.DateTime, index=True, default=datetime.utcnow) user_id = db.Column(db.Integer, db.ForeignKey('user.id'))

    def __repr__(self): return '<Post {}>'.format(self.body)
  • #280 Miguel Grinberg said 2019-05-14T10:14:27Z

    @Igor: Yes, the FlaskForm class accesses the form fields in the flask request object. If it finds anything in request.forms, then it loads that into the form object.

  • #281 Miguel Grinberg said 2019-05-14T10:42:03Z

    @Karl: what do you get when you type "u" in your Python prompt?

  • #282 CarlosR said 2019-05-15T05:53:50Z

    File "/home/pc/microblog/app/init.py", line 14, in from app import routes, models File "/home/pc/microblog/app/routes.py", line 19 @app.route('/login', methods=['GET', 'POST']) ^ IndentationError: expected an indented block (venv) pc-@pc-HP-Pavilion-dm1:~/microblog$

    Hello Miguel, in the middle of part 5 and getting indent errors. I confirmed that tabs and spaces were reset and still getting an error on the routes.py @app.route('/login', methods=['GET', 'POST']) What reference do you suggest I look into? Thank you -

  • #283 Miguel Grinberg said 2019-05-15T09:07:53Z

    @CarlosR: this is probably caused by a mistake in the line above the one with the error. Sometimes Python cannot accurately detect where the error is. If in doubt, compare your code against mine. The download link is at the top of the article.

  • #284 Jurugo Brian said 2019-06-27T08:37:39Z

    From the routes file, when you remove the user template data and render the template, I expected you to give the post variable a value from the model/database because when you leave it as posts=posts, what does posts on the right hand side refer to?

  • #285 Miguel Grinberg said 2019-06-27T14:24:58Z

    @Jurugo: for the posts you should leave the fake list for now. It will be removed later.

  • #286 Jurugo Brian said 2019-07-05T13:23:16Z

    When I attempt entering my password, I get the following error from index.html page. ""File "/home/jurugo/Documents/marolemodel/app/templates/index.html", line 5, in block "content" {% for post in posts %} TypeError: 'DefaultMeta' object is not iterable

  • #287 Miguel Grinberg said 2019-07-05T17:03:49Z

    @Jurugo: check how you set the "posts" argument to render_template. You are passing the wrong thing there.

  • #288 Jared said 2019-07-16T21:43:14Z

    I can't seem to get passed Part V: "Showing the Logged in User Templates".

    Here is the error I get when I 'flask run' at that point:

    Exception: No user_loader has been installed for this LoginManager. Refer tohttps://flask-login.readthedocs.io/en/latest/#how-it-works for more info.

    I made sure I did everything correctly and I did quite a bit of research and I still can't get it to work.

    Does anyone have any suggestions? Thank you in advance.

  • #289 Miguel Grinberg said 2019-07-17T13:41:32Z

    @Jared: the error message that you are getting indicates that you forgot to define a user loader callback for Flask-Login. See the section "User Loader Function" in this article.

  • #290 Tom said 2019-07-17T19:58:53Z

    I kept getting this error, and It would not let me continue.

    return render_template('index.html', title='Home Page', posts=posts)

    I made the change to this: return render_template('index.html', title='Home Page', Post=Post)

    but I'm not sure this is correct even though it is now working.

    any ideas?

  • #291 Miguel Grinberg said 2019-07-17T22:46:42Z

    @Tom: you forgot to include the text of the error that you are getting.

  • #292 ADNLVL said 2019-08-02T21:03:21Z

    Miguel, this blog is fantastic and has allowed me to achieve so much by pulling together an easy python based back end and web based GUI, i've written a few different systems already based on this framework.

    I felt the need to post as i've been attacking my most recent application with Zap to validate the security. I seem to get a lot of false positives regarding sql injection, however I did identify that the code used here to build the login settings is vulnerable to the ' OR '1=1' attack, I was quite astounded when I was able to login to my admin account. I've since resolved this. Any thoughts or comments?

  • #293 Miguel Grinberg said 2019-08-02T21:51:07Z

    @ADNLVL: I don't understand how can you apply the OR 1=1 hack on the login form of this application. Can you give me the step by step? Also, what do you mean by "I was able to login to my admin account"? This application has no admin accounts, right?

  • #294 Mark said 2019-08-16T15:21:31Z

    I have an issue and think i am missing some code when i go to view another users blog it sends an error saying page not found this is when i am logged in and want to view another user this is when i manually enter http://127.0.0.1:5000/user/username. any help would be greatful thanks

  • #295 Miguel Grinberg said 2019-08-16T15:51:29Z

    @Mark: the code for this chapter is available in a download link at the top of this article. You can download it and compare it against yours to find out if you have anything missing.

  • #296 John Hedge said 2019-08-16T20:29:16Z

    Hi Miguel, I've hit a small problem. When I run flask I get: Error: While importing "chouette", an ImportError was raised:

    Traceback (most recent call last): File "d:\users\john\documents\python\project\chouette\env\lib\site-packages\flask\cli.py", line 240, in locate_app import(module_name) File "D:\Users\John\Documents\Python\Project\Chouette\chouette.py", line 1, in from app import app, db File "D:\Users\John\Documents\Python\Project\Chouette\app__init__.py", line 11, in from app import routes, models File "D:\Users\John\Documents\Python\Project\Chouette\app\routes.py", line 5, in from app.forms import LoginForm, RegistrationForm ImportError: cannot import name 'RegistrationForm' from 'app.forms' (D:\Users\John\Documents\Python\Project\Chouette\app\forms.py)

    Line 5 in routes.py is: from app.forms import LoginForm, RegistrationForm (No name 'RegistrationForm' in module 'app.forms'pylint(no-name-in-module)

    I downloaded the zip file of the chapter and pasted it into my files.

    TIA

    John

  • #297 Miguel Grinberg said 2019-08-16T22:59:00Z

    @John: do you have the RegistrationForm class in forms.py? The error suggests you don't.

  • #298 Remy Zandwijk said 2019-08-18T16:24:42Z

    Hi Miguel,

    I bought your book months ago and I just came around working my way through it. It is very well written, thanks!

    In section 'Logging Users Out', the logout function is created. Logging the user out didn't work though, but when I added 'from flask import url_for' to routes.py, it did. Do you agree the import is indeed needed or I am missing something here?

  • #299 Miguel Grinberg said 2019-08-18T17:12:06Z

    @Remy: the url_for import should have been added in routes.py earlier, so it should be on the module already. This is why it isn't included in this part.

  • #300 John Hedge said 2019-08-19T00:26:25Z

    I solved the problem of my last post, Miguel. (White space!)

    Unfortunately I'm unable to get the login to work though. On registering a 'user' the page just hangs.

    John

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