AssertionError: View function mapping is overwriting an existing endpoint function: home - flask

Question

I'm trying to work my way through http://code.tutsplus.com/tutorials/an-introduction-to-pythons-flask-framework--net-28822

C:\envs\virtalenvs\flask_mini\Scripts\python.exe C:/envs/r2/mini2/intro_to_flask/__init__.py
C:\envs\virtalenvs\flask_mini\lib\site-packages\flask_sqlalchemy\__init__.py:800: UserWarning: SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and will be disabled by default in the future.  Set it to True to suppress this warning.
  warnings.warn('SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and will be disabled by default in the future.  Set it to True to suppress this warning.')
Traceback (most recent call last):
  File "C:/envs/r2/mini2/intro_to_flask/__init__.py", line 13, in <module>
    from routes import mail
  File "C:\envs\r2\mini2\intro_to_flask\routes.py", line 9, in <module>
    @app.route('/')
  File "C:\envs\virtalenvs\flask_mini\lib\site-packages\flask\app.py", line 1013, in decorator
    self.add_url_rule(rule, endpoint, f, **options)
  File "C:\envs\virtalenvs\flask_mini\lib\site-packages\flask\app.py", line 62, in wrapper_func
    return f(self, *args, **kwargs)
  File "C:\envs\virtalenvs\flask_mini\lib\site-packages\flask\app.py", line 984, in add_url_rule
    'existing endpoint function: %s' % endpoint)
AssertionError: View function mapping is overwriting an existing endpoint function: home

the routes.py file is:

from intro_to_flask import app
from flask import render_template, request, flash, session, url_for, redirect
from forms import ContactForm, SignupForm, SigninForm
from flask.ext.mail import Message, Mail
from models import db, User

mail = Mail()


@app.route('/')
def home():
    return render_template('home.html')


@app.route('/about')
def about():
    return render_template('about.html')


@app.route('/contact', methods=['GET', 'POST'])
def contact():
    form = ContactForm()

    if request.method == 'POST':
        if form.validate() == False:
            flash('All fields are required.')
            return render_template('contact.html', form=form)
        else:
            msg = Message(form.subject.data, sender='contact@example.com', recipients=['your_email@example.com'])
            msg.body = """
            From: %s <%s>
            %s
            """ % (form.name.data, form.email.data, form.message.data)
            mail.send(msg)

            return render_template('contact.html', success=True)

    elif request.method == 'GET':
        return render_template('contact.html', form=form)


@app.route('/signup', methods=['GET', 'POST'])
def signup():
    form = SignupForm()

    if 'email' in session:
        return redirect(url_for('profile'))

    if request.method == 'POST':
        if form.validate() == False:
            return render_template('signup.html', form=form)
        else:
            newuser = User(form.firstname.data, form.lastname.data, form.email.data, form.password.data)
            db.session.add(newuser)
            db.session.commit()

            session['email'] = newuser.email
            return redirect(url_for('profile'))

    elif request.method == 'GET':
        return render_template('signup.html', form=form)


@app.route('/profile')
def profile():
    if 'email' not in session:
        return redirect(url_for('signin'))

    user = User.query.filter_by(email=session['email']).first()

    if user is None:
        return redirect(url_for('signin'))
    else:
        return render_template('profile.html')


@app.route('/signin', methods=['GET', 'POST'])
def signin():
    form = SigninForm()

    if 'email' in session:
        return redirect(url_for('profile'))

    if request.method == 'POST':
        if form.validate() == False:
            return render_template('signin.html', form=form)
        else:
            session['email'] = form.email.data
            return redirect(url_for('profile'))

    elif request.method == 'GET':
        return render_template('signin.html', form=form)


@app.route('/signout')
def signout():
    if 'email' not in session:
        return redirect(url_for('signin'))

    session.pop('email', None)
    return redirect(url_for('home'))

What could be causing this?

Edit:

When I put the about function first I get:

 AssertionError: View function mapping is overwriting an existing endpoint function: about

So I think the problem may be in the import statements or at least before the first route:

from intro_to_flask import app
from flask import render_template, request, flash, session, url_for, redirect
from forms import ContactForm, SignupForm, SigninForm
from flask.ext.mail import Mail, Message
from models import db, User

mail = Mail()

edit 2:

from flask import Flask

app = Flask(__name__)

app.secret_key = 'development key'

app.config["MAIL_SERVER"] = "smtp.gmail.com"
app.config["MAIL_PORT"] = 465
app.config["MAIL_USE_SSL"] = True
app.config["MAIL_USERNAME"] = 'contact@example.com'
app.config["MAIL_PASSWORD"] = 'your-password'

from routes import mail
mail.init_app(app)

app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql://your-username:your-password@localhost/development'

from models import db
db.init_app(app)

import intro_to_flask.routes

I don't know if this could be related but you have an indentation issue in your `home()` function apparently. — Nicolas, Jan 19 '16 at 13:52
@Nicolas We usually suggest using 4 spaces, right? He mixed 2 and 4 spaces together. — lord63. j, Jan 19 '16 at 14:43
Thanks for pointing that out, i have reformatted to 4 spaces (see above ) but the error is unchanged. — user1592380, Jan 19 '16 at 15:14

score 2 · Accepted Answer · answered Jan 19 '16 at 19:51

This error is because you are cyclic import app (you imported app in routes.py and imported routes.py in app) This pattern doesn't work and is not correct. In flask you can write the whole application in single file or you can use flask blueprints to make in modular http://flask.pocoo.org/docs/0.10/blueprints/

You application can work in a single file:

from flask import render_template, request, flash, session, url_for, redirect
from forms import ContactForm, SignupForm, SigninForm
from flask.ext.mail import Message, Mail
from models import db, User

from flask import Flask

app = Flask(__name__)

app.secret_key = 'development key'

app.config["MAIL_SERVER"] = "smtp.gmail.com"
app.config["MAIL_PORT"] = 465
app.config["MAIL_USE_SSL"] = True
app.config["MAIL_USERNAME"] = 'contact@example.com'
app.config["MAIL_PASSWORD"] = 'your-password'

mail = Mail()

mail.init_app(app)

app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql://your-username:your-password@localhost/development'

from models import db
db.init_app(app)



@app.route('/')
def home():
    return render_template('home.html')


@app.route('/about')
def about():
    return render_template('about.html')


@app.route('/contact', methods=['GET', 'POST'])
def contact():
    form = ContactForm()

    if request.method == 'POST':
        if form.validate() == False:
            flash('All fields are required.')
            return render_template('contact.html', form=form)
        else:
            msg = Message(form.subject.data, sender='contact@example.com', recipients=['your_email@example.com'])
            msg.body = """
            From: %s <%s>
            %s
            """ % (form.name.data, form.email.data, form.message.data)
            mail.send(msg)

            return render_template('contact.html', success=True)

    elif request.method == 'GET':
        return render_template('contact.html', form=form)


@app.route('/signup', methods=['GET', 'POST'])
def signup():
    form = SignupForm()

    if 'email' in session:
        return redirect(url_for('profile'))

    if request.method == 'POST':
        if form.validate() == False:
            return render_template('signup.html', form=form)
        else:
            newuser = User(form.firstname.data, form.lastname.data, form.email.data, form.password.data)
            db.session.add(newuser)
            db.session.commit()

            session['email'] = newuser.email
            return redirect(url_for('profile'))

    elif request.method == 'GET':
        return render_template('signup.html', form=form)


@app.route('/profile')
def profile():
    if 'email' not in session:
        return redirect(url_for('signin'))

    user = User.query.filter_by(email=session['email']).first()

    if user is None:
        return redirect(url_for('signin'))
    else:
        return render_template('profile.html')


@app.route('/signin', methods=['GET', 'POST'])
def signin():
    form = SigninForm()

    if 'email' in session:
        return redirect(url_for('profile'))

    if request.method == 'POST':
        if form.validate() == False:
            return render_template('signin.html', form=form)
        else:
            session['email'] = form.email.data
            return redirect(url_for('profile'))

    elif request.method == 'GET':
        return render_template('signin.html', form=form)


@app.route('/signout')
def signout():
    if 'email' not in session:
        return redirect(url_for('signin'))

    session.pop('email', None)
    return redirect(url_for('home'))

app.run()

Hi itmard, thanks for looking at it. What file do I run? do I delete the __init__.py file? — user1592380, Jan 19 '16 at 21:36
Create a single file containg all of your code and then you can run it. — rezakamalifard, Jan 19 '16 at 21:41
Thank you I commented out everything in init.py and ran routes.py and it worked! — user1592380, Jan 19 '16 at 22:00
Itmard,do you have any advice on deploying to heroku? I'm having problems http://stackoverflow.com/questions/34966616/importerror-no-module-named-flask-on-heroku — user1592380, Jan 24 '16 at 13:00

AssertionError: View function mapping is overwriting an existing endpoint function: home - flask

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