I just finished the Flask basic tutorial (here) and even though I've done completed every step, when I am trying
python flaskr.py
what I get is a 404 Not Found error saying
The requested URL was not found on the server. If you entered the URL manually please check your spelling and try again.
here is the code inside the file
import os
import sqlite3
from flask import Flask, request, session, g, redirect, url_for, abort, render_template, flash
#create app
app = Flask(__name__)
app.config.from_object(__name__)
#load default conf and override config from an env var
app.config.update(dict(
DATABASE=os.path.join(app.root_path, 'flaskr.db'),
DEBUG=True,
SECRET_KEY = 'dev key',
USERNAME = 'admin',
PASSWORD = 'admin'
))
app.config.from_envvar('FLASKR_SETTINGS', silent=True)
def connect_db():
"""connect to the specific db"""
rv = sqlite3.connect(app.config['DATABASE'])
rv.row_factory = sqlite3.Row
return rv
if __name__== '__main__':
app.run()
def get_db():
"""opens a new db connection if there is none yet for the cyrrent app"""
if not hasattr(g, 'sqlite_db'):
g.sqlite_db = connect_db()
return g.sqlite_db
#app.teardown_appcontext
def close_db(error):
"""closes the db again at the end of the request."""
if hasattr(g, 'sqlite_db'):
g.sqlite_db.close()
def init_db():
with app.app_context():
db = get_db()
with app.open_resource('schema.sql', mode='r') as f:
db.cursor().executescript(f.read())
db.commit()
#app.route('/')
def show_entries():
db_get_db()
cur = db.execute('select title, text from entries order by id desc')
entries = cur.fetchall()
return render_template('show_entries.html', entries=entries)
#app.route('/add', methods=['POST'])
def add_entry():
if not session.get('logged_in'):
abort(401)
db = get_db()
db.execute('insert into entries (title, text) values (?,?)',
[request.form['title'], request.form['text']])
db.commit()
flash('New entry was successfully posted')
return redirect(url_for('show_entries'))
#app.route('/login', methods=['GET', 'POST'])
def login():
error = None
if request.method == 'POST':
if request.form['username'] != app.config['USERNAME']:
error = 'Invalid username'
elif request.form['password'] != app.config['PASSWORD']:
error = 'Invalid password'
else:
session['logged_in'] = True
flash('You were logged in')
return redirect(url_for('show_entries'))
return render_template('login.html', error=error)
#app.route('/logout')
def logout():
session.pop('logged_in', None)
flash('You were logged out')
return redirect(url_for('show_entries'))
This is the console message I get (plus 3 attempts to refresh page):
user#user:~/Flask/flaskr$ python flaskr.py
* Running on http://127.0.0.1:5000/
* Restarting with reloader
127.0.0.1 - - [19/Aug/2014 15:23:40] "GET / HTTP/1.1" 404 -
127.0.0.1 - - [19/Aug/2014 15:23:41] "GET / HTTP/1.1" 404 -
127.0.0.1 - - [19/Aug/2014 15:23:42] "GET / HTTP/1.1" 404 -
Any suggestions on what might be going wrong?
You put your app.run() call too early:
if __name__== '__main__':
app.run()
This is executed before any of your routes are registered. Move these two lines to the end of your file.
Next, you have the first line in show_entries() is incorrect:
def show_entries():
db_get_db()
There is no db_get_db() function; this should be db = get_db() instead.
Happened to me also while following Flask Application Setup here . The error was gone after appending a trailing slash at the end of the route.
#app.route('/hello')
def hello():
return 'Hello, World!'
was changed to
#app.route('/hello/')
def hello():
return 'Hello, World!'
and the problem was solved. Hope it helps for anyone who is searching for a problem like this.
You should delete your cache and reload the page.
Press "Ctrl" + "Shift" + "i" to open the developer tools
Right-click on the "reload-icon" (⟳) located to the left of the URL bar
Select "Clear cache and refresh completely"
Related
I am currently in the process of building a flask based LAN chatting app (using sqlite3 to store usernames and socketio for messaging) and am having trouble implementing sessions correctly.
I have followed both this guide:
https://www.techwithtim.net/tutorials/flask/sessions/
and read the documentation here https://flask-session.readthedocs.io/en/latest/ but am somehow still not getting my code to work:
In the login page, when the username is posted, I want users to be redirected to the chat-page.html, but this does not occur. Instead they are redirected to the login page, and I cannot figure out why:
from flask import Flask, render_template, request, flash, session, redirect, url_for
#creating the routes
#app.route('/login', methods=["POST", "GET"])
def login_form():
if request.method == "POST":
username = request.form.get("user_name")
session["user"] = username
return redirect(url_for('chat_page'))
else:
if "user" in session:
return redirect(url_for('chat_page'))
return render_template('login.html')
#app.route('/chat-page')
def chat_page():
if "user" in session:
username = session["user"]
return render_template('chat-page.html', Uname=username)
return redirect(url_for('login_form'))
#app.route("/logout")
def logout():
session.pop("user", None)
flash("You have been logged out!")
return redirect(url_for('login_form'))
from flask_session import Session
app = Flask(__name__)
Session(app)
When I tried to debug your code, I ran into issues with the secret key. I don't know how or where you set it or call your app, but here is my complete code that worked. They key might be to set app.config['SESSION_TYPE'] = 'filesystem'. I used this answer to solve it.
from flask import Flask, render_template, request, flash, session, redirect, url_for
from flask_session import Session
app = Flask(__name__)
app.config['SESSION_TYPE'] = 'filesystem'
app.config['SECRET_KEY'] = 'secret key'
Session(app)
# creating the routes
#app.route('/login', methods=["POST", "GET"])
def login_form():
if request.method == "POST":
username = request.form.get("user_name")
session["user"] = username
return redirect(url_for('chat_page'))
else:
if "user" in session:
return redirect(url_for('chat_page'))
return render_template('login.html')
#app.route('/chat-page')
def chat_page():
if "user" in session:
return '<div>chat page!</div>'
return redirect(url_for('login_form'))
#app.route("/logout")
def logout():
session.pop("user", None)
flash("You have been logged out!")
return redirect(url_for('login_form'))
app.run(debug=True)
What I'm saying is, your redirect logic is completely fine. The issue must be with the session.
Im writing a dummy website for class and I'm having trouble connecting my Heroku Database to my app that's local for now until I push to Heroku.
I'm not sure what the proper way to do this, and I've searched many videos/forums and I can't seem to get a straight answer from them. Ill post some of my code below. In dbconnect.py where the insert the heroku database credentials, like the URI, host, etc?
#app.py
from flask import Flask, render_template, redirect, url_for, request, session, flash
from functools import wraps
app = Flask(__name__)
app.secret_key = "Gundam"
# login required decorator
def login_required(f):
#wraps(f)
def wrap(*args, **kwargs):
if 'logged_in' in session:
return f(*args, **kwargs)
else:
flash('You need to login first.')
return redirect(url_for('login_page'))
return wrap
#app.route('/')
def homepage():
return render_template("main.html")
#app.route('/dashboard/')
#login_required
def dashboard():
return render_template("dashboard.html")
#app.errorhandler(404)
def page_not_found(e):
return render_template("404.html")
#app.route('/login/', methods=["GET", "POST"])
def login_page():
error = ''
try:
if request.method == "POST":
attempted_username = request.form['username']
attempted_password = request.form['password']
if attempted_username == "admin" and attempted_password == "password":
session['logged_in'] = True
flash('You were just logged in!')
return redirect(url_for('dashboard'))
else:
error = "Invalid Username or Password."
return render_template("login.html", error=error)
except Exception as e:
return render_template("login.html", error=error)
#app.route('/logout/')
def logout():
session.pop("logged_in", None)
return redirect(url_for('homepage'))
if __name__ == '__main__':
app.run(debug = True)
dbconnect.py
import os
import psycopg2
import urlparse
urlparse.uses_netloc.append("postgres")
url = urlparse.urlparse(os.environ[""])
conn = psycopg2.connect(
database=url.path[1:],
user=url.username,
password=url.password,
host=url.hostname,
port=url.port
)
You have to install the postgres database addon in heroku first. Run the heroku toolbelt in your computer and enter the command heroku addons:create heroku-postgresql:hobby-dev. Hobby-dev is the free version.
Once Heroku Postgres has been added a DATABASE_URL setting will be available in the app configuration and will contain the URL used to access the newly provisioned Heroku Postgres service. Use the value as your database uri. The app configuration can be accessed from your dashboard. Under settings, click Reveal config vars. You can also use the toolbelt command. See heroku config -h.
So now you can do:
url = urlparse.urlparse(os.environ["DATABASE_URL"])
For more details see https://devcenter.heroku.com/articles/heroku-postgresql
Just use the following code snippet on your python app. That should do the trick.
import os
import psycopg2
DATABASE_URL = os.environ['DATABASE_URL']
conn = psycopg2.connect(DATABASE_URL, sslmode='require')
When I specify an IP and port without the preceding:
if __name__ == '__main__':
As such:
app.run(host="138.165.91.210",port=5017,threaded=True)
It works but it hangs a bit (does it hang on an infinite loop maybe?). When I do the usual:
if __name__ == '__main__':
app.run(host="138.165.91.210",port=5017,threaded=True)
It avoids the ip and port. What's wrong with my code?
Full script:
import os
from sqlite3 import dbapi2 as sqlite3
from flask import Flask, request, session, g, redirect, url_for, abort, \
render_template, flash
# create our little application :)
app = Flask(__name__)
# Load default config and override config from an environment variable
def connect_db():
"""Connects to the specific database."""
rv = sqlite3.connect(app.config['DATABASE'])
rv.row_factory = sqlite3.Row
return rv
def init_db():
"""Initializes the database."""
db = get_db()
with app.open_resource('schema.sql', mode='r') as f:
db.cursor().executescript(f.read())
db.commit()
#app.cli.command('initdb')
def initdb_command():
"""Creates the database tables."""
init_db()
print('Initialized the database.')
def get_db():
"""Opens a new database connection if there is none yet for the
current application context.
"""
if not hasattr(g, 'sqlite_db'):
g.sqlite_db = connect_db()
return g.sqlite_db
#app.teardown_appcontext
def close_db(error):
"""Closes the database again at the end of the request."""
if hasattr(g, 'sqlite_db'):
g.sqlite_db.close()
#app.route('/')
def show_entries():
db = get_db()
cur = db.execute('select title, text from entries order by id desc')
entries = cur.fetchall()
return render_template('show_entries.html', entries=entries)
#app.route('/add', methods=['POST'])
def add_entry():
if not session.get('logged_in'):
abort(401)
db = get_db()
db.execute('insert into entries (title, text) values (?, ?)',
[request.form['title'], request.form['text']])
db.commit()
flash('New entry was successfully posted')
return redirect(url_for('show_entries'))
#app.route('/login', methods=['GET', 'POST'])
def login():
error = None
if request.method == 'POST':
if request.form['username'] != app.config['USERNAME']:
error = 'Invalid username'
elif request.form['password'] != app.config['PASSWORD']:
error = 'Invalid password'
else:
session['logged_in'] = True
flash('You were logged in')
return redirect(url_for('show_entries'))
return render_template('login.html', error=error)
#app.route('/logout')
def logout():
session.pop('logged_in', None)
flash('You were logged out')
return redirect(url_for('show_entries'))
#app.route("/hello")
def hello():
return "Hello World!"
if __name__ == '__main__':
app.run(host="138.165.91.210",port=5017,threaded=True)
Edit:
I'm running the app using bash:
flask --app=flaskr run
You are using an unreleased version of Flask, so keep in mind that things might change.
__name__ == '__main__' only evaluates to True when you execute a file directly (i.e., python filename.py). Since that isn't how you're running it here, it will be False and that block is skipped.
To solve your port issue, when running your application using the flask command, you need to specify your options through the command line.
python -m flask --app flaskr --host 138.165.91.210 --port 5017 --with-threads
For more information, you should check the usage
python -m flask --help
To solve your delay issue, the if __name__ == '__main__': block is important. Without it, Flask will try to run two instances of the application (once from the flask command and one from the call to app.run).
I have built a website using flask (www.csppdb.com). Sometimes when I log in as one user, log out, then login as another user I still see pages from the first user I logged in as. This problem is immediately fixed when the page is refreshed. I think this is called "caching" if I am not mistaken. Is there any way I could disable this on a site wide level so that every page that is visited needs a new refresh?
It would be like sharing your computer with a friend. He logs into Facebook, then logs out. Now you log in on his computer and you see his profile... (awkward). After you refresh the page the problem is fixed.
Here is some of my code. I was using flask-login but I then tried to "roll my own"
from flask.ext.mysql import MySQL
import os
from flask import Flask, request, jsonify, session, url_for, redirect, \
render_template, g, flash
from data import *
from werkzeug import check_password_hash, generate_password_hash
import config
app = Flask(__name__)
mysql = MySQL()
app.config['MYSQL_DATABASE_HOST'] = os.environ['MYSQL_DATABASE_HOST'] if 'MYSQL_DATABASE_HOST' in os.environ else config.MYSQL_DATABASE_HOST
app.config['MYSQL_DATABASE_PORT'] = os.environ['MYSQL_DATABASE_PORT'] if 'MYSQL_DATABASE_PORT' in os.environ else config.MYSQL_DATABASE_PORT
app.config['MYSQL_DATABASE_USER'] = os.environ['MYSQL_DATABASE_USER'] if 'MYSQL_DATABASE_USER' in os.environ else config.MYSQL_DATABASE_USER
app.config['MYSQL_DATABASE_PASSWORD'] = os.environ['MYSQL_DATABASE_PASSWORD'] if 'MYSQL_DATABASE_PASSWORD' in os.environ else config.MYSQL_DATABASE_PASSWORD
app.config['MYSQL_DATABASE_DB'] = os.environ['MYSQL_DATABASE_DB'] if 'MYSQL_DATABASE_DB' in os.environ else config.MYSQL_DATABASE_DB
mysql.init_app(app)
if 'SECRET_KEY' in os.environ: app.config['SECRET_KEY'] = os.environ['SECRET_KEY']
else: app.config['SECRET_KEY'] = os.urandom(24)
def connect_db(): return mysql.connect()
def check_auth():
g.user = None
if 'username' in session:
g.user = get_user(session['username'])
return
return redirect(url_for('login'))
#app.route('/')
def home():
if 'username' in session: return redirect(url_for('main'))
return render_template('home.html')
def connect_db(): return mysql.connect()
#app.teardown_request
def teardown_request(exception):
if exception: print exception
g.db.close()
#app.before_request
def before_request():
print session.keys(), session.values()
print("before request")
print ('username' in session, "in session?")
g.db = connect_db()
g.user = None
if "username" in session:
g.user = get_user(session['username'])
#app.route('/login/', methods=['GET', 'POST'])
def login():
"""Logs the user in."""
if 'username' in session:
return redirect(url_for('main'))
error = None
if request.method == 'POST':
print("login hit")
user = get_user(request.form['username'])
if user is None:
error = 'Invalid username'
print error
elif not check_password_hash(user.password, request.form['password']):
error = 'Invalid password'
print error
else:
flash('You were logged in')
print "logged in"
session['username'] = request.form['username']
g.user = request.form['username']
print error, "error"
return redirect(url_for('main'))
return render_template('login.html', error=error)
Setting the cache to be max-age=0 fixed it.
#app.after_request
def add_header(response):
"""
Add headers to both force latest IE rendering engine or Chrome Frame,
and also to cache the rendered page for 10 minutes.
"""
response.headers['X-UA-Compatible'] = 'IE=Edge,chrome=1'
response.headers['Cache-Control'] = 'public, max-age=0'
return response
To stop browser caching on these sort of pages you need to set some HTTP response headers.
Cache-Control: no-cache, no-store
Pragma: no-cache
Once you do this then the browser wont cache those pages. I dont know how to do this with "flask" so I will leave that as an exercise for you :)
This question shows how to add a response header Flask/Werkzeug how to attach HTTP content-length header to file download
I have a sample web application (flask with flask-login running on heroku) at this URL: http://twittaclone.herokuapp.com.
When I run it on my localhost the login functionality works fine. When I push to heroku it freaks out and does not allow users to login (it does allow user registration). Database modifications are being made.
Why would flask login not work on heroku?
app = Flask(__name__)
mysql = MySQL()
app.config['MYSQL_DATABASE_HOST'] = os.environ['MYSQL_DATABASE_HOST'] if 'MYSQL_DATABASE_HOST' in os.environ else config.MYSQL_DATABASE_HOST
app.config['MYSQL_DATABASE_PORT'] = os.environ['MYSQL_DATABASE_PORT'] if 'MYSQL_DATABASE_PORT' in os.environ else config.MYSQL_DATABASE_PORT
app.config['MYSQL_DATABASE_USER'] = os.environ['MYSQL_DATABASE_USER'] if 'MYSQL_DATABASE_USER' in os.environ else config.MYSQL_DATABASE_USER
app.config['MYSQL_DATABASE_PASSWORD'] = os.environ['MYSQL_DATABASE_PASSWORD'] if 'MYSQL_DATABASE_PASSWORD' in os.environ else config.MYSQL_DATABASE_PASSWORD
app.config['MYSQL_DATABASE_DB'] = os.environ['MYSQL_DATABASE_DB'] if 'MYSQL_DATABASE_DB' in os.environ else config.MYSQL_DATABASE_DB
mysql.init_app(app)
if 'SECRET_KEY' in os.environ: app.config['SECRET_KEY'] = os.environ['SECRET_KEY']
else: app.config['SECRET_KEY'] = os.urandom(24)
def connect_db(): return mysql.connect()
###
# Routing for your application.
###
login_manager = LoginManager()
login_manager.login_view = "login"
#login_manager.user_loader
def load_user(username):
g.db = connect_db()
return get_user(username)
login_manager.init_app(app)
#app.route('/')
def home(): return render_template('home.html')
def connect_db(): return mysql.connect()
#app.before_request
def before_request():
g.user = current_user
g.db = connect_db()
#app.teardown_request
def tear_down(exception):
g.db.close()
#app.route('/main/')
#login_required
def main():
print("in main")
tweets, user = get_main()
follower_count, followee_count = get_follower_info(g.user.username)
return render_template('main.html', user=user, tweets=tweets, followercount = follower_count, followeecount = followee_count)
#app.route('/login/', methods=['GET', 'POST'])
def login():
"""Logs the user in."""
if request.method == 'GET':
if current_user is user_logged_in: logout_user()
error = None
if request.method == 'POST':
user = get_user(request.form['username'])
if user is None:
error = 'Invalid username'
elif not check_password_hash(user.password, request.form['password']):
error = 'Invalid password'
else:
flash('You were logged in')
login_user(user)
return redirect(url_for('main'))
return render_template('login.html', error=error)
Many years later but this solves your issue: Heroku gunicorn flask login is not working properly
Updated Procfile:
web: gunicorn app:app --preload
Documentation on preloading for gunicorn: https://docs.gunicorn.org/en/stable/settings.html
I'm pretty sure that Heroku uses PostgreSQL. Try referring to their documents https://devcenter.heroku.com/articles/heroku-postgresql