Develop Reference

First time creating a website with Flask, I keep coming up with 'Error: No such command 'init-db' when creating a database

I'm following this tutorial, but have still managed to mess it up. Go figure.
Done everything up to the third page where we create the database. I know init-db is the correct format, I have installed flask within the venv, and I have no idea where I went wrong.
Edit: I have done the exports
db.py
import sqlite3
import click
from flask import current_app, g
from flask.cli import with_appcontext
def get_db():
if 'db' not in g:
g.db = sqlite3.connect(
current_app.config['DATABASE'],
detect_types=sqlite3.PARSE_DECLTYPES
)
g.db.row_factory = sqlite3.Row
return g.db
def close_db(e=None):
db = g.pop('db', None)
if db is not None:
db.close()
def init_db():
db = get_db()
with current_app.open_resource('schema.sql') as f:
db.executescript(f.read().decode('utf8'))
#click.command('init-db')
#with_appcontext
def init_db_command():
#clear the existing data and create new tables
init_db()
click.echo('Initialized the database.')
def init_app(app):
app.teardown_appcontext(close_db)
app.cli.add_command(init_db_command)
init.py
import os
from flask import Flask
def create_app(test_config=None):
app = Flask(__name__, instance_relative_config=True)
app.config.from_mapping(
SECRET_KEY='dev',
DATABASE=os.path.join(app.instance_path, 'flaskr.sqlite'),
)
if test_config is None:
app.config.from_pyfile('config.py', silent=True)
else:
app.config.from_mapping(test_config)
try:
os.makedirs(app.instance_path)
except OSError:
pass
#app.route('/hello')
def hello():
return 'Hello World'
from . import db
db.init_app(app)
return app
and schema.sql
DROP TABLE IF EXISTS user;
DROP TABLE IF EXISTS post;
CREATE TABLE user (
id INTEGER PRIMARY KEY AUTOINCREMENT,
username TEXT UNIQUE NOT NULL,
password TEXT NOT NULL
);
CREATE TABLE post (
id INTEGER PRIMARY KEY AUTOINCREMENT,
author_id INTEGER NOT NULL,
created TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
title TEXT NOT NULL,
body TEXT NOT NULL,
FOREIGN KEY (author_id) REFERENCES user (id)
);
complete error code:
(venv) root#pi:/home/pi/flaskr# flask init-db
Usage: flask [OPTIONS] COMMAND [ARGS]...
Try 'flask --help' for help.
Error: No such command 'init-db'.

So.. This took a while for me to recreate, however I have figured it out. You are in the wrong directory in your terminal. flask init-db needs to be ran from pi not flaskr... this is assuming that your venv environment is in pi.

flask error with SQLAlchemy / ORM -- not seeing db tables

In development (so sqlite3) I'm getting this error on any database access:
sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) no such table: ujs ...
I got here by saying
export FLASK_ENV=development
export FLASK_APP=my_app.py
flask db init
flask db migrate
flask db upgrade
flask run
and then doing an HTTP GET against that dev server.
I believe the migration workflow succeeded, because when I use the sqlite3 commandline client, I can see the (empty) table with a believably correct schema.
╭╴ (get-db-working *%=)╶╮
╰ jeff#starshine:TN_flask_web $ sqlite3 dev.db
SQLite version 3.27.2 2019-02-25 16:06:06
Enter ".help" for usage hints.
sqlite> .table
alembic_version ujs
sqlite> .quit
╭╴ (get-db-working *%=)╶╮
╰ jeff#starshine:TN_flask_web $
I therefore believe I've made a coding error. But I'm not seeing it.
I have this code (pared down to what I believe is the essential bits):
my_app.py:
from app import create_app, db, cli
from app.models import UJS
app = create_app()
cli.register(app)
#app.shell_context_processor
def make_shell_context():
return {'db': db,
'UJS': UJS}
app/models.py:
from app import db
import time
def now_in_microseconds():
"""Return the current time in microseconds since the epoch.
"""
return time.time() * 1000 * 1000
class UJS(db.Model):
id = db.Column(db.Integer, primary_key=True)
timestamp_microseconds = db.Column(db.BigInteger, default=now_in_microseconds)
ip_hash = db.column(db.String(40))
# And then some more columns, all quite boring.
def __repr__(self):
return '<[{tag}]/[{ip}] {microsec}/{city}>'.format(
tag=self.tag, ip=self.ip_hash,
microsec=self.timestamp_microseconds, city=self.city)
app/__init__.py:
from flask import Flask, request, current_app
from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate
from config import Config
db = SQLAlchemy()
migrate = Migrate()
def create_app(config_class=Config):
app = Flask(__name__)
app.config.from_object(config_class)
try:
app.config.from_pyfile("../config_local.py")
except FileNotFoundError:
print('No local config found.')
except:
print('Unexpected error on app.config.from_pyfile()')
db.init_app(app)
migrate.init_app(app, db)
...
return app
from app import models
and app/main/routes.py:
from flask import request, g, current_app, session
from app import db
from app.main import bp
from app.models import UJS
#bp.before_app_request
def before_request():
if 'static' == request.endpoint:
# This should only happen in dev. Otherwise, nginx handles static routes directly.
return
# I expect this to return an empty list, but it throws a 500.
print(UJS.query.all())
Any suggestions what I'm missing?

For anyone who might find this question later on: the problem was about having the right absolute path to your DB in your SQLALCHEMY_DATABASE_URI config value.
Also (this wasnt the case here, but it might possibly gotcha with the same symptoms) - if you omit __tablename__ on Model declaration, SQLAlchemy might autogenerate something you wont expect. Just a thing to keep in mind, if you're working with an existing DB with some schema already in place.

How to close db with flask_mongoengine?

I am learning to use flask and flask_mongoengine to create a website. Follow the flask tutorial 1.0.2 version. But I ran into a problem, how to implement the get_db() and close_db() function?
Currently, what I am doing is :
myapp.py
....
def create_app():
app = Flask(__name__)
from db import db
db.init_app(app)
#app.route('/')
def home():
...
return app
db.py
from flask import g
from flask_mongoengine import MongoEngine
db = MongoEngine()
def get_db():
g.db = ???
return g.db
def close_db():
db = g.pop('db', None)
if db is not None:
??? # db.close() doesn't exist!!!
I am very confused about how to do this part. Can someone give any suggestions? In flask_mongoengine tutorial page, they don't implement the get_db() and close_db() ...

Confusion happens because in those tutorials there are too many programming patterns. In flask-1.0.2 tutorial they use getter method pattern and but flask-mongoengine relies on bootstraping a db to flask-app-instance, which relies on a builder pattern — Flask Application Factories. It may still be confusing but I'll show you how it's meant to be done.
Bootstrap a flask-mongoengine in create_app:
def create_app(test_config=None):
app = Flask(__name__)
# configure mongo settings here like in flask-mongoengine docs
g.db = db = MongoEngine()
db.init_app(app)
def get_db():
return g.db
def close_db():
pass
What's about close_db()? Well, that function exists in case db you've chosen needs some cleanup actions to be closed. But I haven't found in mongoengine docs any explicit mention that mongoengine db connection need a cleanup actions from you to be closed, so you can just pass it.

Flask tutorial: AttributeError teardown_appcontext

I'm a beginner of Python and Flask.
I was going through Flask tutorial up to "Define and Access the Database" section.
Wrote up all codes, saved, and did below on Windows command prompt.
flask init-db
However, got received the error on the command prompt as follows.
AttributeError: 'ellipsis' object has no attribute 'teardown_appcontext'
I doublechecked the codes to confirm it's written exactly in a way that tutorial specifies and it actually worked fine until the previous section.
Searched through Stackoverflows if there is any similar questions, but ended up not finding out a clear cause.
Any advises? Thank you very much for your support.
--Additions--
Thanks Joost. Here is what I did.
Files layout image link
__init__.py
import os
from flask import Flask
def create_app(test_config=None):
# create and configure the app
app = Flask(__name__, instance_relative_config=True)
app.config.from_mapping(
SECRET_KEY='dev',
DATABASE=os.path.join(app.instance_path, 'flaskr.sqlite'),
)
if test_config is None:
# Load the instance config, if it exists, when not testing
app.config.from_pyfile('config.py', silent=True)
else:
# Load the test config if passed in
app.config.from_mapping(test_config)
# ensure the instance floder exists
try:
os.makedirs(app.instance_path)
except OSError:
pass
# a simple page that says hello
#app.route('/hello')
def hello():
return 'Hello, World!'
def create_app():
app = ...
# existing code omitted
from . import db
db.init_app(app)
return app
db.py
import sqlite3
import click
from flask import current_app, g
from flask.cli import with_appcontext
def get_db():
if 'db' not in g:
g.db = sqlite3.connect(
current_app.config['DATABASE'],
detect_types=sqlite3.PARSE_DECLTYPES
)
g.db.row_factory = sqlite3.Row
return g.db
def close_db(e=None):
db = g.pop('db', None)
if db is not None:
db.close()
def init_db():
db = get_db()
with current_app.open_resource('schema.sql') as f:
db.executescript(f.read().decode('utf8'))
#click.command('init-db')
#with_appcontext
def init_db_command():
"""Clear the exisitng data and create new tables."""
init_db()
click.echo('Initialized the database.')
def init_app(app):
app.teardown_appcontext(close_db)
app.cli.add_command(init_db_command)
schema.sql
DROP TABLE IF EXISTS user;
DROP TABLE IF EXISTS post;
CREATE TABLE user (
id INTEGER PRIMARY KEY AUTOINCREMENT,
username TEXT UNIQUE NOT NULL,
password TEXT NOT NULL
);
CREATE TABLE post (
id INTEGER PRIMARY KEY AUTOINCREMENT,
author_id INTEGER NOT NULL,
created TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
title TEXT NOT NULL,
body TEXT NOT NULL,
FOREIGN KEY (author_id) REFERENCES user (id)
);
And finally I did on the command prompt:
set FLASK_APP=flaskr
set FLASK_ENV=development
flask init-db
However it returned like this.
Any advises?
Thank you very much.

You defined create_app() twice. To solve your problem, make the following change in your __init__.py files:
import os
from flask import Flask
def create_app(test_config=None):
""" Application factory function """
# create and configure the app
app = Flask(__name__, instance_relative_config=True)
app.config.from_mapping(
SECRET_KEY='dev',
DATABASE=os.path.join(app.instance_path, 'flaskr.sqlite'),
)
if test_config is None:
# load the instance config, if it exists, when not testing
app.config.from_pyfile('config.py', silent=True)
else:
# load the test config if passed in
app.config.from_mapping(test_config)
# ensure the instance folder exists
try:
os.makedirs(app.instance_path)
except OSError:
pass
# a simple page that says hello
#app.route('/hello')
def hello():
return 'Hello, World! Now We are Introducing Mr. Narendra Singh Parihar.THE BOSS !!'
from . import db
db.init_app(app)
return app

Actually the problem is in your init.py
I removed the second create_app() from your init file and edited it like below remember the app factory need to know where your db.py is while creating the app
import os
from flask import Flask
def create_app(test_config=None):
# create and configure the app
app = Flask(__name__, instance_relative_config=True)
app.config.from_mapping(
SECRET_KEY='dev',
DATABASE=os.path.join(app.instance_path, 'flaskr.sqlite'),
)
if test_config is None:
# Load the instance config, if it exists, when not testing
app.config.from_pyfile('config.py', silent=True)
else:
# Load the test config if passed in
app.config.from_mapping(test_config)
# ensure the instance floder exists
try:
os.makedirs(app.instance_path)
except OSError:
pass
# a simple page that says hello
#app.route('/hello')
def hello():
return 'Hello, World!'
from . import db
db.init_app(app)
return app

you don't replace the existing code with the new proposed one,
but you add to it,
so for example :
def create_app():
app = ...
# existing code omitted
from . import db
db.init_app(app)
return app
should be translated in your code by adding the two new lines :
from . import db
db.init_app(app)
to what's already there so far in the function, just before the last line.
return app
which should translate as other answers mentioned :
def create_app(test_config=None):
# create and configure the app
app = Flask(__name__, instance_relative_config=True)
app.config.from_mapping(
SECRET_KEY='dev',
DATABASE=os.path.join(app.instance_path, 'flaskr.sqlite'),
)
if test_config is None:
# Load the instance config, if it exists, when not testing
app.config.from_pyfile('config.py', silent=True)
else:
# Load the test config if passed in
app.config.from_mapping(test_config)
# ensure the instance floder exists
try:
os.makedirs(app.instance_path)
except OSError:
pass
# a simple page that says hello
#app.route('/hello')
def hello():
return 'Hello, World!'
from . import db
db.init_app(app)
return app

How to use Flask with mysql (without sqlalchemy - raw sql query)?

I'm learning Flask framework. How to use Flask with mysql (without sqlalchemy - raw sql query)?
Here is example from official tutorial, how to configure it to use mysql?
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
app.config.update(dict(
DATABASE='/tmp/firma.db',
DEBUG=True,
SECRET_KEY='development key',
USERNAME='admin',
PASSWORD='default'
))
app.config.from_envvar('FIRMA_SETTINGS', silent=True)
def connect_db():
"""Connects to the specific database."""
rv = sqlite3.connect(app.config['DATABASE'])
rv.row_factory = sqlite3.Row
return rv
def init_db():
"""Creates the database tables."""
with app.app_context():
db = get_db()
with app.open_resource('firma.sql', mode='r') as f:
db.cursor().executescript(f.read())
db.commit()
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)
...
How to configure it to use mysql?

You need a mysql driver. Python doesn't come with one by default. You'll have to install a 3rd party library like MySQLdb. Even if you use an ORM like sqlalchemy, you'll still need to install the driver. Also, you can run raw SQL with sqlalchemy.