Welcome to Flask¶

text/html

$ mkdir myproject
$ cd myproject
$ python3 -m venv venv

$ py -3 -m venv venv

$ python2 -m virtualenv venv

> \Python27\Scripts\virtualenv.exe venv

$ . venv/bin/activate

> venv\Scripts\activate

$ pip install Flask

$ pip install -U https://github.com/pallets/flask/archive/master.tar.gz

# Debian, Ubuntu
$ sudo apt-get install python-virtualenv

# CentOS, Fedora
$ sudo yum install python-virtualenv

# Arch
$ sudo pacman -S python-virtualenv

$ sudo python2 Downloads/get-pip.py
$ sudo python2 -m pip install virtualenv

> \Python27\python.exe Downloads\get-pip.py
> \Python27\python.exe -m pip install virtualenv

from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello, World!'

$ export FLASK_APP=hello.py
$ flask run
 * Running on http://127.0.0.1:5000/

C:\path\to\app>set FLASK_APP=hello.py

PS C:\path\to\app> $env:FLASK_APP = "hello.py"

$ export FLASK_APP=hello.py
$ python -m flask run
 * Running on http://127.0.0.1:5000/

$ flask run --host=0.0.0.0

$ export FLASK_ENV=development
$ flask run

@app.route('/')
def index():
    return 'Index Page'

@app.route('/hello')
def hello():
    return 'Hello, World'

from markupsafe import escape

@app.route('/user/<username>')
def show_user_profile(username):
    # show the user profile for that user
    return 'User %s' % escape(username)

@app.route('/post/<int:post_id>')
def show_post(post_id):
    # show the post with the given id, the id is an integer
    return 'Post %d' % post_id

@app.route('/path/<path:subpath>')
def show_subpath(subpath):
    # show the subpath after /path/
    return 'Subpath %s' % escape(subpath)

@app.route('/projects/')
def projects():
    return 'The project page'

@app.route('/about')
def about():
    return 'The about page'

from flask import Flask, url_for
from markupsafe import escape

app = Flask(__name__)

@app.route('/')
def index():
    return 'index'

@app.route('/login')
def login():
    return 'login'

@app.route('/user/<username>')
def profile(username):
    return '{}\'s profile'.format(escape(username))

with app.test_request_context():
    print(url_for('index'))
    print(url_for('login'))
    print(url_for('login', next='/'))
    print(url_for('profile', username='John Doe'))

/
/login
/login?next=/
/user/John%20Doe

from flask import request

@app.route('/login', methods=['GET', 'POST'])
def login():
    if request.method == 'POST':
        return do_the_login()
    else:
        return show_the_login_form()

url_for('static', filename='style.css')

from flask import render_template

@app.route('/hello/')
@app.route('/hello/<name>')
def hello(name=None):
    return render_template('hello.html', name=name)

/application.py
/templates
    /hello.html

/application
    /__init__.py
    /templates
        /hello.html

<!doctype html>
<title>Hello from Flask</title>
{% if name %}
  <h1>Hello {{ name }}!</h1>
{% else %}
  <h1>Hello, World!</h1>
{% endif %}

>>> from markupsafe import Markup
>>> Markup('<strong>Hello %s!</strong>') % '<blink>hacker</blink>'
Markup(u'<strong>Hello &lt;blink&gt;hacker&lt;/blink&gt;!</strong>')
>>> Markup.escape('<blink>hacker</blink>')
Markup(u'&lt;blink&gt;hacker&lt;/blink&gt;')
>>> Markup('<em>Marked up</em> &raquo; HTML').striptags()
u'Marked up \xbb HTML'

from flask import request

with app.test_request_context('/hello', method='POST'):
    # now you can do something with the request until the
    # end of the with block, such as basic assertions:
    assert request.path == '/hello'
    assert request.method == 'POST'

from flask import request

with app.request_context(environ):
    assert request.method == 'POST'

from flask import request

@app.route('/login', methods=['POST', 'GET'])
def login():
    error = None
    if request.method == 'POST':
        if valid_login(request.form['username'],
                       request.form['password']):
            return log_the_user_in(request.form['username'])
        else:
            error = 'Invalid username/password'
    # the code below is executed if the request method
    # was GET or the credentials were invalid
    return render_template('login.html', error=error)

searchword = request.args.get('key', '')

from flask import request

@app.route('/upload', methods=['GET', 'POST'])
def upload_file():
    if request.method == 'POST':
        f = request.files['the_file']
        f.save('/var/www/uploads/uploaded_file.txt')
    ...

from flask import request
from werkzeug.utils import secure_filename

@app.route('/upload', methods=['GET', 'POST'])
def upload_file():
    if request.method == 'POST':
        f = request.files['the_file']
        f.save('/var/www/uploads/' + secure_filename(f.filename))
    ...

from flask import request

@app.route('/')
def index():
    username = request.cookies.get('username')
    # use cookies.get(key) instead of cookies[key] to not get a
    # KeyError if the cookie is missing.

from flask import make_response

@app.route('/')
def index():
    resp = make_response(render_template(...))
    resp.set_cookie('username', 'the username')
    return resp

from flask import abort, redirect, url_for

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

@app.route('/login')
def login():
    abort(401)
    this_is_never_executed()

from flask import render_template

@app.errorhandler(404)
def page_not_found(error):
    return render_template('page_not_found.html'), 404

@app.errorhandler(404)
def not_found(error):
    return render_template('error.html'), 404

@app.errorhandler(404)
def not_found(error):
    resp = make_response(render_template('error.html'), 404)
    resp.headers['X-Something'] = 'A value'
    return resp

@app.route("/me")
def me_api():
    user = get_current_user()
    return {
        "username": user.username,
        "theme": user.theme,
        "image": url_for("user_image", filename=user.image),
    }

@app.route("/users")
def users_api():
    users = get_all_users()
    return jsonify([user.to_json() for user in users])

from flask import Flask, session, redirect, url_for, request
from markupsafe import escape

app = Flask(__name__)

# Set the secret key to some random bytes. Keep this really secret!
app.secret_key = b'_5#y2L"F4Q8z\n\xec]/'

@app.route('/')
def index():
    if 'username' in session:
        return 'Logged in as %s' % escape(session['username'])
    return 'You are not logged in'

@app.route('/login', methods=['GET', 'POST'])
def login():
    if request.method == 'POST':
        session['username'] = request.form['username']
        return redirect(url_for('index'))
    return '''
        <form method="post">
            <p><input type=text name=username>
            <p><input type=submit value=Login>
        </form>
    '''

@app.route('/logout')
def logout():
    # remove the username from the session if it's there
    session.pop('username', None)
    return redirect(url_for('index'))

$ python -c 'import os; print(os.urandom(16))'
b'_5#y2L"F4Q8z\n\xec]/'

app.logger.debug('A value for debugging')
app.logger.warning('A warning occurred (%d apples)', 42)
app.logger.error('An error occurred')

from werkzeug.middleware.proxy_fix import ProxyFix
app.wsgi_app = ProxyFix(app.wsgi_app)

$ mkdir flask-tutorial
$ cd flask-tutorial

from flask import Flask

app = Flask(__name__)

@app.route('/')
def hello():
    return 'Hello, World!'

/home/user/Projects/flask-tutorial
├── flaskr/
│   ├── __init__.py
│   ├── db.py
│   ├── schema.sql
│   ├── auth.py
│   ├── blog.py
│   ├── templates/
│   │   ├── base.html
│   │   ├── auth/
│   │   │   ├── login.html
│   │   │   └── register.html
│   │   └── blog/
│   │       ├── create.html
│   │       ├── index.html
│   │       └── update.html
│   └── static/
│       └── style.css
├── tests/
│   ├── conftest.py
│   ├── data.sql
│   ├── test_factory.py
│   ├── test_db.py
│   ├── test_auth.py
│   └── test_blog.py
├── venv/
├── setup.py
└── MANIFEST.in

venv/

*.pyc
__pycache__/

instance/

.pytest_cache/
.coverage
htmlcov/

dist/
build/
*.egg-info/

$ mkdir flaskr

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 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!'

    return app

$ export FLASK_APP=flaskr
$ export FLASK_ENV=development
$ flask run

> set FLASK_APP=flaskr
> set FLASK_ENV=development
> flask run

> $env:FLASK_APP = "flaskr"
> $env:FLASK_ENV = "development"
> flask run

* Serving Flask app "flaskr"
* Environment: development
* Debug mode: on
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
* Restarting with stat
* Debugger is active!
* Debugger PIN: 855-212-761

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()

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)
);

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)

def create_app():
    app = ...
    # existing code omitted

    from . import db
    db.init_app(app)

    return app

$ flask init-db
Initialized the database.

import functools

from flask import (
    Blueprint, flash, g, redirect, render_template, request, session, url_for
)
from werkzeug.security import check_password_hash, generate_password_hash

from flaskr.db import get_db

bp = Blueprint('auth', __name__, url_prefix='/auth')

def create_app():
    app = ...
    # existing code omitted

    from . import auth
    app.register_blueprint(auth.bp)

    return app

@bp.route('/register', methods=('GET', 'POST'))
def register():
    if request.method == 'POST':
        username = request.form['username']
        password = request.form['password']
        db = get_db()
        error = None

        if not username:
            error = 'Username is required.'
        elif not password:
            error = 'Password is required.'
        elif db.execute(
            'SELECT id FROM user WHERE username = ?', (username,)
        ).fetchone() is not None:
            error = 'User {} is already registered.'.format(username)

        if error is None:
            db.execute(
                'INSERT INTO user (username, password) VALUES (?, ?)',
                (username, generate_password_hash(password))
            )
            db.commit()
            return redirect(url_for('auth.login'))

        flash(error)

    return render_template('auth/register.html')

@bp.route('/login', methods=('GET', 'POST'))
def login():
    if request.method == 'POST':
        username = request.form['username']
        password = request.form['password']
        db = get_db()
        error = None
        user = db.execute(
            'SELECT * FROM user WHERE username = ?', (username,)
        ).fetchone()

        if user is None:
            error = 'Incorrect username.'
        elif not check_password_hash(user['password'], password):
            error = 'Incorrect password.'

        if error is None:
            session.clear()
            session['user_id'] = user['id']
            return redirect(url_for('index'))

        flash(error)

    return render_template('auth/login.html')

@bp.before_app_request
def load_logged_in_user():
    user_id = session.get('user_id')

    if user_id is None:
        g.user = None
    else:
        g.user = get_db().execute(
            'SELECT * FROM user WHERE id = ?', (user_id,)
        ).fetchone()

@bp.route('/logout')
def logout():
    session.clear()
    return redirect(url_for('index'))

def login_required(view):
    @functools.wraps(view)
    def wrapped_view(**kwargs):
        if g.user is None:
            return redirect(url_for('auth.login'))

        return view(**kwargs)

    return wrapped_view

<!doctype html>
<title>{% block title %}{% endblock %} - Flaskr</title>
<link rel="stylesheet" href="{{ url_for('static', filename='style.css') }}">
<nav>
  <h1>Flaskr</h1>
  <ul>
    {% if g.user %}
      <li><span>{{ g.user['username'] }}</span>
      <li><a href="{{ url_for('auth.logout') }}">Log Out</a>
    {% else %}
      <li><a href="{{ url_for('auth.register') }}">Register</a>
      <li><a href="{{ url_for('auth.login') }}">Log In</a>
    {% endif %}
  </ul>
</nav>
<section class="content">
  <header>
    {% block header %}{% endblock %}
  </header>
  {% for message in get_flashed_messages() %}
    <div class="flash">{{ message }}</div>
  {% endfor %}
  {% block content %}{% endblock %}
</section>

{% extends 'base.html' %}

{% block header %}
  <h1>{% block title %}Register{% endblock %}</h1>
{% endblock %}

{% block content %}
  <form method="post">
    <label for="username">Username</label>
    <input name="username" id="username" required>
    <label for="password">Password</label>
    <input type="password" name="password" id="password" required>
    <input type="submit" value="Register">
  </form>
{% endblock %}

{% extends 'base.html' %}

{% block header %}
  <h1>{% block title %}Log In{% endblock %}</h1>
{% endblock %}

{% block content %}
  <form method="post">
    <label for="username">Username</label>
    <input name="username" id="username" required>
    <label for="password">Password</label>
    <input type="password" name="password" id="password" required>
    <input type="submit" value="Log In">
  </form>
{% endblock %}

{{ url_for('static', filename='style.css') }}

html { font-family: sans-serif; background: #eee; padding: 1rem; }
body { max-width: 960px; margin: 0 auto; background: white; }
h1 { font-family: serif; color: #377ba8; margin: 1rem 0; }
a { color: #377ba8; }
hr { border: none; border-top: 1px solid lightgray; }
nav { background: lightgray; display: flex; align-items: center; padding: 0 0.5rem; }
nav h1 { flex: auto; margin: 0; }
nav h1 a { text-decoration: none; padding: 0.25rem 0.5rem; }
nav ul  { display: flex; list-style: none; margin: 0; padding: 0; }
nav ul li a, nav ul li span, header .action { display: block; padding: 0.5rem; }
.content { padding: 0 1rem 1rem; }
.content > header { border-bottom: 1px solid lightgray; display: flex; align-items: flex-end; }
.content > header h1 { flex: auto; margin: 1rem 0 0.25rem 0; }
.flash { margin: 1em 0; padding: 1em; background: #cae6f6; border: 1px solid #377ba8; }
.post > header { display: flex; align-items: flex-end; font-size: 0.85em; }
.post > header > div:first-of-type { flex: auto; }
.post > header h1 { font-size: 1.5em; margin-bottom: 0; }
.post .about { color: slategray; font-style: italic; }
.post .body { white-space: pre-line; }
.content:last-child { margin-bottom: 0; }
.content form { margin: 1em 0; display: flex; flex-direction: column; }
.content label { font-weight: bold; margin-bottom: 0.5em; }
.content input, .content textarea { margin-bottom: 1em; }
.content textarea { min-height: 12em; resize: vertical; }
input.danger { color: #cc2f2e; }
input[type=submit] { align-self: start; min-width: 10em; }

from flask import (
    Blueprint, flash, g, redirect, render_template, request, url_for
)
from werkzeug.exceptions import abort

from flaskr.auth import login_required
from flaskr.db import get_db

bp = Blueprint('blog', __name__)

def create_app():
    app = ...
    # existing code omitted

    from . import blog
    app.register_blueprint(blog.bp)
    app.add_url_rule('/', endpoint='index')

    return app

@bp.route('/')
def index():
    db = get_db()
    posts = db.execute(
        'SELECT p.id, title, body, created, author_id, username'
        ' FROM post p JOIN user u ON p.author_id = u.id'
        ' ORDER BY created DESC'
    ).fetchall()
    return render_template('blog/index.html', posts=posts)

{% extends 'base.html' %}

{% block header %}
  <h1>{% block title %}Posts{% endblock %}</h1>
  {% if g.user %}
    <a class="action" href="{{ url_for('blog.create') }}">New</a>
  {% endif %}
{% endblock %}

{% block content %}
  {% for post in posts %}
    <article class="post">
      <header>
        <div>
          <h1>{{ post['title'] }}</h1>
          <div class="about">by {{ post['username'] }} on {{ post['created'].strftime('%Y-%m-%d') }}</div>
        </div>
        {% if g.user['id'] == post['author_id'] %}
          <a class="action" href="{{ url_for('blog.update', id=post['id']) }}">Edit</a>
        {% endif %}
      </header>
      <p class="body">{{ post['body'] }}</p>
    </article>
    {% if not loop.last %}
      <hr>
    {% endif %}
  {% endfor %}
{% endblock %}

@bp.route('/create', methods=('GET', 'POST'))
@login_required
def create():
    if request.method == 'POST':
        title = request.form['title']
        body = request.form['body']
        error = None

        if not title:
            error = 'Title is required.'

        if error is not None:
            flash(error)
        else:
            db = get_db()
            db.execute(
                'INSERT INTO post (title, body, author_id)'
                ' VALUES (?, ?, ?)',
                (title, body, g.user['id'])
            )
            db.commit()
            return redirect(url_for('blog.index'))

    return render_template('blog/create.html')

{% extends 'base.html' %}

{% block header %}
  <h1>{% block title %}New Post{% endblock %}</h1>
{% endblock %}

{% block content %}
  <form method="post">
    <label for="title">Title</label>
    <input name="title" id="title" value="{{ request.form['title'] }}" required>
    <label for="body">Body</label>
    <textarea name="body" id="body">{{ request.form['body'] }}</textarea>
    <input type="submit" value="Save">
  </form>
{% endblock %}

def get_post(id, check_author=True):
    post = get_db().execute(
        'SELECT p.id, title, body, created, author_id, username'
        ' FROM post p JOIN user u ON p.author_id = u.id'
        ' WHERE p.id = ?',
        (id,)
    ).fetchone()

    if post is None:
        abort(404, "Post id {0} doesn't exist.".format(id))

    if check_author and post['author_id'] != g.user['id']:
        abort(403)

    return post

@bp.route('/<int:id>/update', methods=('GET', 'POST'))
@login_required
def update(id):
    post = get_post(id)

    if request.method == 'POST':
        title = request.form['title']
        body = request.form['body']
        error = None

        if not title:
            error = 'Title is required.'

        if error is not None:
            flash(error)
        else:
            db = get_db()
            db.execute(
                'UPDATE post SET title = ?, body = ?'
                ' WHERE id = ?',
                (title, body, id)
            )
            db.commit()
            return redirect(url_for('blog.index'))

    return render_template('blog/update.html', post=post)

{% extends 'base.html' %}

{% block header %}
  <h1>{% block title %}Edit "{{ post['title'] }}"{% endblock %}</h1>
{% endblock %}

{% block content %}
  <form method="post">
    <label for="title">Title</label>
    <input name="title" id="title"
      value="{{ request.form['title'] or post['title'] }}" required>
    <label for="body">Body</label>
    <textarea name="body" id="body">{{ request.form['body'] or post['body'] }}</textarea>
    <input type="submit" value="Save">
  </form>
  <hr>
  <form action="{{ url_for('blog.delete', id=post['id']) }}" method="post">
    <input class="danger" type="submit" value="Delete" onclick="return confirm('Are you sure?');">
  </form>
{% endblock %}

@bp.route('/<int:id>/delete', methods=('POST',))
@login_required
def delete(id):
    get_post(id)
    db = get_db()
    db.execute('DELETE FROM post WHERE id = ?', (id,))
    db.commit()
    return redirect(url_for('blog.index'))

from setuptools import find_packages, setup

setup(
    name='flaskr',
    version='1.0.0',
    packages=find_packages(),
    include_package_data=True,
    zip_safe=False,
    install_requires=[
        'flask',
    ],
)

include flaskr/schema.sql
graft flaskr/static
graft flaskr/templates
global-exclude *.pyc

$ pip install -e .

$ pip list

Package        Version   Location
-------------- --------- ----------------------------------
click          6.7
Flask          1.0
flaskr         1.0.0     /home/user/Projects/flask-tutorial
itsdangerous   0.24
Jinja2         2.10
MarkupSafe     1.0
pip            9.0.3
setuptools     39.0.1
Werkzeug       0.14.1
wheel          0.30.0

$ pip install pytest coverage

INSERT INTO user (username, password)
VALUES
  ('test', 'pbkdf2:sha256:50000$TCI4GzcX$0de171a4f4dac32e3364c7ddc7c14f3e2fa61f2d17574483f7ffbb431b4acb2f'),
  ('other', 'pbkdf2:sha256:50000$kJPKsz6N$d2d4784f1b030a9761f5ccaeeaca413f27f2ecb76d6168407af962ddce849f79');

INSERT INTO post (title, body, author_id, created)
VALUES
  ('test title', 'test' || x'0a' || 'body', 1, '2018-01-01 00:00:00');

import os
import tempfile

import pytest
from flaskr import create_app
from flaskr.db import get_db, init_db

with open(os.path.join(os.path.dirname(__file__), 'data.sql'), 'rb') as f:
    _data_sql = f.read().decode('utf8')

@pytest.fixture
def app():
    db_fd, db_path = tempfile.mkstemp()

    app = create_app({
        'TESTING': True,
        'DATABASE': db_path,
    })

    with app.app_context():
        init_db()
        get_db().executescript(_data_sql)

    yield app

    os.close(db_fd)
    os.unlink(db_path)

@pytest.fixture
def client(app):
    return app.test_client()

@pytest.fixture
def runner(app):
    return app.test_cli_runner()

from flaskr import create_app

def test_config():
    assert not create_app().testing
    assert create_app({'TESTING': True}).testing

def test_hello(client):
    response = client.get('/hello')
    assert response.data == b'Hello, World!'

import sqlite3

import pytest
from flaskr.db import get_db

def test_get_close_db(app):
    with app.app_context():
        db = get_db()
        assert db is get_db()

    with pytest.raises(sqlite3.ProgrammingError) as e:
        db.execute('SELECT 1')

    assert 'closed' in str(e.value)

def test_init_db_command(runner, monkeypatch):
    class Recorder(object):
        called = False

    def fake_init_db():
        Recorder.called = True

    monkeypatch.setattr('flaskr.db.init_db', fake_init_db)
    result = runner.invoke(args=['init-db'])
    assert 'Initialized' in result.output
    assert Recorder.called

class AuthActions(object):
    def __init__(self, client):
        self._client = client

    def login(self, username='test', password='test'):
        return self._client.post(
            '/auth/login',
            data={'username': username, 'password': password}
        )

    def logout(self):
        return self._client.get('/auth/logout')

@pytest.fixture
def auth(client):
    return AuthActions(client)

import pytest
from flask import g, session
from flaskr.db import get_db

def test_register(client, app):
    assert client.get('/auth/register').status_code == 200
    response = client.post(
        '/auth/register', data={'username': 'a', 'password': 'a'}
    )
    assert 'http://localhost/auth/login' == response.headers['Location']

    with app.app_context():
        assert get_db().execute(
            "select * from user where username = 'a'",
        ).fetchone() is not None

@pytest.mark.parametrize(('username', 'password', 'message'), (
    ('', '', b'Username is required.'),
    ('a', '', b'Password is required.'),
    ('test', 'test', b'already registered'),
))
def test_register_validate_input(client, username, password, message):
    response = client.post(
        '/auth/register',
        data={'username': username, 'password': password}
    )
    assert message in response.data

def test_login(client, auth):
    assert client.get('/auth/login').status_code == 200
    response = auth.login()
    assert response.headers['Location'] == 'http://localhost/'

    with client:
        client.get('/')
        assert session['user_id'] == 1
        assert g.user['username'] == 'test'

@pytest.mark.parametrize(('username', 'password', 'message'), (
    ('a', 'test', b'Incorrect username.'),
    ('test', 'a', b'Incorrect password.'),
))
def test_login_validate_input(auth, username, password, message):
    response = auth.login(username, password)
    assert message in response.data

def test_logout(client, auth):
    auth.login()

    with client:
        auth.logout()
        assert 'user_id' not in session

import pytest
from flaskr.db import get_db

def test_index(client, auth):
    response = client.get('/')
    assert b"Log In" in response.data
    assert b"Register" in response.data

    auth.login()
    response = client.get('/')
    assert b'Log Out' in response.data
    assert b'test title' in response.data
    assert b'by test on 2018-01-01' in response.data
    assert b'test\nbody' in response.data
    assert b'href="/1/update"' in response.data

@pytest.mark.parametrize('path', (
    '/create',
    '/1/update',
    '/1/delete',
))
def test_login_required(client, path):
    response = client.post(path)
    assert response.headers['Location'] == 'http://localhost/auth/login'

def test_author_required(app, client, auth):
    # change the post author to another user
    with app.app_context():
        db = get_db()
        db.execute('UPDATE post SET author_id = 2 WHERE id = 1')
        db.commit()

    auth.login()
    # current user can't modify other user's post
    assert client.post('/1/update').status_code == 403
    assert client.post('/1/delete').status_code == 403
    # current user doesn't see edit link
    assert b'href="/1/update"' not in client.get('/').data

@pytest.mark.parametrize('path', (
    '/2/update',
    '/2/delete',
))
def test_exists_required(client, auth, path):
    auth.login()
    assert client.post(path).status_code == 404

def test_create(client, auth, app):
    auth.login()
    assert client.get('/create').status_code == 200
    client.post('/create', data={'title': 'created', 'body': ''})

    with app.app_context():
        db = get_db()
        count = db.execute('SELECT COUNT(id) FROM post').fetchone()[0]
        assert count == 2

def test_update(client, auth, app):
    auth.login()
    assert client.get('/1/update').status_code == 200
    client.post('/1/update', data={'title': 'updated', 'body': ''})

    with app.app_context():
        db = get_db()
        post = db.execute('SELECT * FROM post WHERE id = 1').fetchone()
        assert post['title'] == 'updated'

@pytest.mark.parametrize('path', (
    '/create',
    '/1/update',
))
def test_create_update_validate(client, auth, path):
    auth.login()
    response = client.post(path, data={'title': '', 'body': ''})
    assert b'Title is required.' in response.data

def test_delete(client, auth, app):
    auth.login()
    response = client.post('/1/delete')
    assert response.headers['Location'] == 'http://localhost/'

    with app.app_context():
        db = get_db()
        post = db.execute('SELECT * FROM post WHERE id = 1').fetchone()
        assert post is None

[tool:pytest]
testpaths = tests

[coverage:run]
branch = True
source =
    flaskr

$ pytest

========================= test session starts ==========================
platform linux -- Python 3.6.4, pytest-3.5.0, py-1.5.3, pluggy-0.6.0
rootdir: /home/user/Projects/flask-tutorial, inifile: setup.cfg
collected 23 items

tests/test_auth.py ........                                      [ 34%]
tests/test_blog.py ............                                  [ 86%]
tests/test_db.py ..                                              [ 95%]
tests/test_factory.py ..                                         [100%]

====================== 24 passed in 0.64 seconds =======================

$ coverage run -m pytest

$ coverage report

Name                 Stmts   Miss Branch BrPart  Cover
------------------------------------------------------
flaskr/__init__.py      21      0      2      0   100%
flaskr/auth.py          54      0     22      0   100%
flaskr/blog.py          54      0     16      0   100%
flaskr/db.py            24      0      4      0   100%
------------------------------------------------------
TOTAL                  153      0     44      0   100%

$ coverage html

$ pip install wheel

$ python setup.py bdist_wheel

$ pip install flaskr-1.0.0-py3-none-any.whl

$ export FLASK_APP=flaskr
$ flask init-db

$ python -c 'import os; print(os.urandom(16))'

b'_5#y2L"F4Q8z\n\xec]/'

SECRET_KEY = b'_5#y2L"F4Q8z\n\xec]/'

$ pip install waitress

$ waitress-serve --call 'flaskr:create_app'

Serving on http://0.0.0.0:8080

{% from '_helpers.html' import my_macro with context %}

<script type=text/javascript>
    doSomethingWith({{ user.username|tojson }});
</script>

<button onclick='doSomethingWith({{ user.username|tojson }})'>
    Click me
</button>

{% autoescape false %}
    <p>autoescaping is disabled here
    <p>{{ will_not_be_escaped }}
{% endautoescape %}

@app.template_filter('reverse')
def reverse_filter(s):
    return s[::-1]

def reverse_filter(s):
    return s[::-1]
app.jinja_env.filters['reverse'] = reverse_filter

{% for x in mylist | reverse %}
{% endfor %}

@app.context_processor
def inject_user():
    return dict(user=g.user)

@app.context_processor
def utility_processor():
    def format_price(amount, currency=u'€'):
        return u'{0:.2f}{1}'.format(amount, currency)
    return dict(format_price=format_price)

{{ format_price(0.33) }}

$ pip install pytest

import os
import tempfile

import pytest

from flaskr import flaskr

@pytest.fixture
def client():
    db_fd, flaskr.app.config['DATABASE'] = tempfile.mkstemp()
    flaskr.app.config['TESTING'] = True

    with flaskr.app.test_client() as client:
        with flaskr.app.app_context():
            flaskr.init_db()
        yield client

    os.close(db_fd)
    os.unlink(flaskr.app.config['DATABASE'])

$ pytest

================ test session starts ================
rootdir: ./flask/examples/flaskr, inifile: setup.cfg
collected 0 items

=========== no tests ran in 0.07 seconds ============

def test_empty_db(client):
    """Start with a blank database."""

    rv = client.get('/')
    assert b'No entries here so far' in rv.data

$ pytest -v

================ test session starts ================
rootdir: ./flask/examples/flaskr, inifile: setup.cfg
collected 1 items

tests/test_flaskr.py::test_empty_db PASSED

============= 1 passed in 0.10 seconds ==============

def login(client, username, password):
    return client.post('/login', data=dict(
        username=username,
        password=password
    ), follow_redirects=True)

def logout(client):
    return client.get('/logout', follow_redirects=True)

def test_login_logout(client):
    """Make sure login and logout works."""

    rv = login(client, flaskr.app.config['USERNAME'], flaskr.app.config['PASSWORD'])
    assert b'You were logged in' in rv.data

    rv = logout(client)
    assert b'You were logged out' in rv.data

    rv = login(client, flaskr.app.config['USERNAME'] + 'x', flaskr.app.config['PASSWORD'])
    assert b'Invalid username' in rv.data

    rv = login(client, flaskr.app.config['USERNAME'], flaskr.app.config['PASSWORD'] + 'x')
    assert b'Invalid password' in rv.data

def test_messages(client):
    """Test that messages work."""

    login(client, flaskr.app.config['USERNAME'], flaskr.app.config['PASSWORD'])
    rv = client.post('/add', data=dict(
        title='<Hello>',
        text='<strong>HTML</strong> allowed here'
    ), follow_redirects=True)
    assert b'No entries here so far' not in rv.data
    assert b'&lt;Hello&gt;' in rv.data
    assert b'<strong>HTML</strong> allowed here' in rv.data

$ pytest -v

================ test session starts ================
rootdir: ./flask/examples/flaskr, inifile: setup.cfg
collected 3 items

tests/test_flaskr.py::test_empty_db PASSED
tests/test_flaskr.py::test_login_logout PASSED
tests/test_flaskr.py::test_messages PASSED

============= 3 passed in 0.23 seconds ==============

import flask

app = flask.Flask(__name__)

with app.test_request_context('/?name=Peter'):
    assert flask.request.path == '/'
    assert flask.request.args['name'] == 'Peter'

app = flask.Flask(__name__)

with app.test_request_context('/?name=Peter'):
    app.preprocess_request()
    ...

app = flask.Flask(__name__)

with app.test_request_context('/?name=Peter'):
    resp = Response('...')
    resp = app.process_response(resp)
    ...

def get_user():
    user = getattr(g, 'user', None)
    if user is None:
        user = fetch_current_user_from_database()
        g.user = user
    return user

from contextlib import contextmanager
from flask import appcontext_pushed, g

@contextmanager
def user_set(app, user):
    def handler(sender, **kwargs):
        g.user = user
    with appcontext_pushed.connected_to(handler, app):
        yield

from flask import json, jsonify

@app.route('/users/me')
def users_me():
    return jsonify(username=g.user.username)

with user_set(app, my_user):
    with app.test_client() as c:
        resp = c.get('/users/me')
        data = json.loads(resp.data)
        self.assert_equal(data['username'], my_user.username)

app = flask.Flask(__name__)

with app.test_client() as c:
    rv = c.get('/?tequila=42')
    assert request.args['tequila'] == '42'

with app.test_client() as c:
    rv = c.get('/')
    assert flask.session['foo'] == 42

with app.test_client() as c:
    with c.session_transaction() as sess:
        sess['a_key'] = 'a value'

    # once this is reached the session was stored and ready to be used by the client
    c.get(...)

from flask import request, jsonify

@app.route('/api/auth')
def auth():
    json_data = request.get_json()
    email = json_data['email']
    password = json_data['password']
    return jsonify(token=generate_token(email, password))

with app.test_client() as c:
    rv = c.post('/api/auth', json={
        'email': 'flask@example.com', 'password': 'secret'
    })
    json_data = rv.get_json()
    assert verify_token(email, json_data['token'])

import click

@app.cli.command('hello')
@click.option('--name', default='World')
def hello_command(name):
    click.echo(f'Hello, {name}!')

def test_hello():
    runner = app.test_cli_runner()

    # invoke the command directly
    result = runner.invoke(hello_command, ['--name', 'Flask'])
    assert 'Hello, Flask' in result.output

    # or by name
    result = runner.invoke(args=['hello'])
    assert 'World' in result.output

def upper(ctx, param, value):
    if value is not None:
        return value.upper()

@app.cli.command('hello')
@click.option('--name', default='World', callback=upper)
def hello_command(name):
    click.echo(f'Hello, {name}!')

def test_hello_params():
    context = hello_command.make_context('hello', ['--name', 'flask'])
    assert context.params['name'] == 'FLASK'

$ pip install sentry-sdk[flask]

import sentry_sdk
from sentry_sdk.integrations.flask import FlaskIntegration

sentry_sdk.init('YOUR_DSN_HERE',integrations=[FlaskIntegration()])

@app.errorhandler(werkzeug.exceptions.BadRequest)
def handle_bad_request(e):
    return 'bad request!', 400

# or, without the decorator
app.register_error_handler(400, handle_bad_request)

class InsufficientStorage(werkzeug.exceptions.HTTPException):
    code = 507
    description = 'Not enough storage space.'

app.register_error_handler(InsufficientStorage, handle_507)

raise InsufficientStorage()

from flask import json
from werkzeug.exceptions import HTTPException

@app.errorhandler(HTTPException)
def handle_exception(e):
    """Return JSON instead of HTML for HTTP errors."""
    # start with the correct headers and status code from the error
    response = e.get_response()
    # replace the body with JSON
    response.data = json.dumps({
        "code": e.code,
        "name": e.name,
        "description": e.description,
    })
    response.content_type = "application/json"
    return response

from werkzeug.exceptions import HTTPException

@app.errorhandler(Exception)
def handle_exception(e):
    # pass through HTTP errors
    if isinstance(e, HTTPException):
        return e

    # now you're handling non-HTTP exceptions only
    return render_template("500_generic.html", e=e), 500

@app.errorhandler(InternalServerError)
def handle_500(e):
    original = getattr(e, "original_exception", None)

    if original is None:
        # direct 500 error, such as abort(500)
        return render_template("500.html"), 500

    # wrapped unhandled error
    return render_template("500_unhandled.html", e=original), 500

FLASK:
    DEBUG: True
    DEBUG_WITH_APTANA: True

if __name__ == "__main__":
    # To allow aptana to receive errors, set use_debugger=False
    app = create_app(config="config.yaml")

    use_debugger = app.debug and not(app.config.get('DEBUG_WITH_APTANA'))
    app.run(use_debugger=use_debugger, debug=app.debug,
            use_reloader=use_debugger, host='0.0.0.0')

@app.route('/login', methods=['POST'])
def login():
    user = get_user(request.form['username'])

    if user.check_password(request.form['password']):
        login_user(user)
        app.logger.info('%s logged in successfully', user.username)
        return redirect(url_for('index'))
    else:
        app.logger.info('%s failed to log in', user.username)
        abort(401)

from logging.config import dictConfig

dictConfig({
    'version': 1,
    'formatters': {'default': {
        'format': '[%(asctime)s] %(levelname)s in %(module)s: %(message)s',
    }},
    'handlers': {'wsgi': {
        'class': 'logging.StreamHandler',
        'stream': 'ext://flask.logging.wsgi_errors_stream',
        'formatter': 'default'
    }},
    'root': {
        'level': 'INFO',
        'handlers': ['wsgi']
    }
})

app = Flask(__name__)

from flask.logging import default_handler

app.logger.removeHandler(default_handler)

import logging
from logging.handlers import SMTPHandler

mail_handler = SMTPHandler(
    mailhost='127.0.0.1',
    fromaddr='server-error@example.com',
    toaddrs=['admin@example.com'],
    subject='Application Error'
)
mail_handler.setLevel(logging.ERROR)
mail_handler.setFormatter(logging.Formatter(
    '[%(asctime)s] %(levelname)s in %(module)s: %(message)s'
))

if not app.debug:
    app.logger.addHandler(mail_handler)

from flask import has_request_context, request
from flask.logging import default_handler

class RequestFormatter(logging.Formatter):
    def format(self, record):
        if has_request_context():
            record.url = request.url
            record.remote_addr = request.remote_addr
        else:
            record.url = None
            record.remote_addr = None

        return super().format(record)

formatter = RequestFormatter(
    '[%(asctime)s] %(remote_addr)s requested %(url)s\n'
    '%(levelname)s in %(module)s: %(message)s'
)
default_handler.setFormatter(formatter)
mail_handler.setFormatter(formatter)

from flask.logging import default_handler

root = logging.getLogger()
root.addHandler(default_handler)
root.addHandler(mail_handler)

for logger in (
    app.logger,
    logging.getLogger('sqlalchemy'),
    logging.getLogger('other_package'),
):
    logger.addHandler(default_handler)
    logger.addHandler(mail_handler)

app = Flask(__name__)
app.config['TESTING'] = True

app.testing = True

app.config.update(
    TESTING=True,
    SECRET_KEY=b'_5#y2L"F4Q8z\n\xec]/'
)

$ export FLASK_ENV=development
$ flask run

$ python -c 'import os; print(os.urandom(16))'
b'_5#y2L"F4Q8z\n\xec]/'

127.0.0.1 localhost.dev

app = Flask(__name__)
app.config.from_object('yourapplication.default_settings')
app.config.from_envvar('YOURAPPLICATION_SETTINGS')

$ export YOURAPPLICATION_SETTINGS=/path/to/settings.cfg
$ python run-app.py
 * Running on http://127.0.0.1:5000/
 * Restarting with reloader...

> set YOURAPPLICATION_SETTINGS=\path\to\settings.cfg

# Example configuration
DEBUG = False
SECRET_KEY = b'_5#y2L"F4Q8z\n\xec]/'

$ export SECRET_KEY='5f352379324c22463451387a0aec5d2f'
$ export MAIL_ENABLED=false
$ python run-app.py
 * Running on http://127.0.0.1:5000/

> set SECRET_KEY='5f352379324c22463451387a0aec5d2f'

import os

_mail_enabled = os.environ.get("MAIL_ENABLED", default="true")
MAIL_ENABLED = _mail_enabled.lower() in {"1", "t", "true"}

SECRET_KEY = os.environ.get("SECRET_KEY")

if not SECRET_KEY:
    raise ValueError("No SECRET_KEY set for Flask application")

app = Flask(__name__)
app.config.from_object('yourapplication.default_settings')
app.config.from_envvar('YOURAPPLICATION_SETTINGS')

class Config(object):
    DEBUG = False
    TESTING = False
    DATABASE_URI = 'sqlite:///:memory:'

class ProductionConfig(Config):
    DATABASE_URI = 'mysql://user@localhost/foo'

class DevelopmentConfig(Config):
    DEBUG = True

class TestingConfig(Config):
    TESTING = True

app.config.from_object('configmodule.ProductionConfig')

from configmodule import ProductionConfig
app.config.from_object(ProductionConfig())

# Alternatively, import via string:
from werkzeug.utils import import_string
cfg = import_string('configmodule.ProductionConfig')()
app.config.from_object(cfg)

class Config(object):
    """Base config, uses staging database server."""
    DEBUG = False
    TESTING = False
    DB_SERVER = '192.168.1.56'

    @property
    def DATABASE_URI(self):         # Note: all caps
        return 'mysql://user@{}/foo'.format(self.DB_SERVER)

class ProductionConfig(Config):
    """Uses production database server."""
    DB_SERVER = '192.168.19.32'

class DevelopmentConfig(Config):
    DB_SERVER = 'localhost'
    DEBUG = True

class TestingConfig(Config):
    DB_SERVER = 'localhost'
    DEBUG = True
    DATABASE_URI = 'sqlite:///:memory:'

app = Flask(__name__, instance_path='/path/to/instance/folder')

/myapp.py
/instance

/myapp
    /__init__.py
/instance

$PREFIX/lib/python2.X/site-packages/myapp
$PREFIX/var/myapp-instance

app = Flask(__name__, instance_relative_config=True)

app = Flask(__name__, instance_relative_config=True)
app.config.from_object('yourapplication.default_settings')
app.config.from_pyfile('application.cfg', silent=True)

filename = os.path.join(app.instance_path, 'application.cfg')
with open(filename) as f:
    config = f.read()

# or via open_instance_resource:
with app.open_instance_resource('application.cfg') as f:
    config = f.read()

from flask import template_rendered
from contextlib import contextmanager

@contextmanager
def captured_templates(app):
    recorded = []
    def record(sender, template, context, **extra):
        recorded.append((template, context))
    template_rendered.connect(record, app)
    try:
        yield recorded
    finally:
        template_rendered.disconnect(record, app)

with captured_templates(app) as templates:
    rv = app.test_client().get('/')
    assert rv.status_code == 200
    assert len(templates) == 1
    template, context = templates[0]
    assert template.name == 'index.html'
    assert len(context['items']) == 10

from flask import template_rendered

def captured_templates(app, recorded, **extra):
    def record(sender, template, context):
        recorded.append((template, context))
    return template_rendered.connected_to(record, app)

templates = []
with captured_templates(app, templates, **extra):
    ...
    template, context = templates[0]

from blinker import Namespace
my_signals = Namespace()

model_saved = my_signals.signal('model-saved')

class Model(object):
    ...

    def save(self):
        model_saved.send(self)

from flask import template_rendered

@template_rendered.connect_via(app)
def when_template_rendered(sender, template, context, **extra):
    print 'Template %s is rendered with %s' % (template.name, context)

@app.route('/users/')
def show_users(page):
    users = User.query.all()
    return render_template('users.html', users=users)

from flask.views import View

class ShowUsers(View):

    def dispatch_request(self):
        users = User.query.all()
        return render_template('users.html', objects=users)

app.add_url_rule('/users/', view_func=ShowUsers.as_view('show_users'))

from flask.views import View

class ListView(View):

    def get_template_name(self):
        raise NotImplementedError()

    def render_template(self, context):
        return render_template(self.get_template_name(), **context)

    def dispatch_request(self):
        context = {'objects': self.get_objects()}
        return self.render_template(context)

class UserView(ListView):

    def get_template_name(self):
        return 'users.html'

    def get_objects(self):
        return User.query.all()

class RenderTemplateView(View):
    def __init__(self, template_name):
        self.template_name = template_name
    def dispatch_request(self):
        return render_template(self.template_name)

app.add_url_rule('/about', view_func=RenderTemplateView.as_view(
    'about_page', template_name='about.html'))

class MyView(View):
    methods = ['GET', 'POST']

    def dispatch_request(self):
        if request.method == 'POST':
            ...
        ...

app.add_url_rule('/myview', view_func=MyView.as_view('myview'))

from flask.views import MethodView

class UserAPI(MethodView):

    def get(self):
        users = User.query.all()
        ...

    def post(self):
        user = User.from_form_data(request.form)
        ...

app.add_url_rule('/users/', view_func=UserAPI.as_view('users'))

def user_required(f):
    """Checks whether user is logged in or raises error 401."""
    def decorator(*args, **kwargs):
        if not g.user:
            abort(401)
        return f(*args, **kwargs)
    return decorator

view = user_required(UserAPI.as_view('users'))
app.add_url_rule('/users/', view_func=view)

class UserAPI(MethodView):
    decorators = [user_required]

class UserAPI(MethodView):

    def get(self, user_id):
        if user_id is None:
            # return a list of users
            pass
        else:
            # expose a single user
            pass

    def post(self):
        # create a new user
        pass

    def delete(self, user_id):
        # delete a single user
        pass

    def put(self, user_id):
        # update a single user
        pass

user_view = UserAPI.as_view('user_api')
app.add_url_rule('/users/', defaults={'user_id': None},
                 view_func=user_view, methods=['GET',])
app.add_url_rule('/users/', view_func=user_view, methods=['POST',])
app.add_url_rule('/users/<int:user_id>', view_func=user_view,
                 methods=['GET', 'PUT', 'DELETE'])

def register_api(view, endpoint, url, pk='id', pk_type='int'):
    view_func = view.as_view(endpoint)
    app.add_url_rule(url, defaults={pk: None},
                     view_func=view_func, methods=['GET',])
    app.add_url_rule(url, view_func=view_func, methods=['POST',])
    app.add_url_rule('%s<%s:%s>' % (url, pk_type, pk), view_func=view_func,
                     methods=['GET', 'PUT', 'DELETE'])

register_api(UserAPI, 'user_api', '/users/', pk='user_id')

RuntimeError: Working outside of application context.

This typically means that you attempted to use functionality that
needed to interface with the current application object in some way.
To solve this, set up an application context with app.app_context().

def create_app():
    app = Flask(__name__)

    with app.app_context():
        init_db()

    return app

from flask import g

def get_db():
    if 'db' not in g:
        g.db = connect_to_database()

    return g.db

@app.teardown_appcontext
def teardown_db(exception):
    db = g.pop('db', None)

    if db is not None:
        db.close()

from werkzeug.local import LocalProxy
db = LocalProxy(get_db)

RuntimeError: Working outside of request context.

This typically means that you attempted to use functionality that
needed an active HTTP request. Consult the documentation on testing
for information about how to avoid this problem.

def generate_report(year):
    format = request.args.get('format')
    ...

with app.test_request_context(
        '/make_report/2017', data={'format': 'short'}):
    generate_report()

from flask import Flask, request

app = Flask(__name__)

@app.route('/')
def hello():
    print('during view')
    return 'Hello, World!'

@app.teardown_request
def show_teardown(exception):
    print('after with block')

with app.test_request_context():
    print('during with block')

# teardown functions are called after the context with block exits

with app.test_client() as client:
    client.get('/')
    # the contexts are not popped even though the request ended
    print(request.path)

# the contexts are popped and teardown functions are called after
# the client with block exits

app = current_app._get_current_object()
my_signal.send(app)

from flask import Blueprint, render_template, abort
from jinja2 import TemplateNotFound

simple_page = Blueprint('simple_page', __name__,
                        template_folder='templates')

@simple_page.route('/', defaults={'page': 'index'})
@simple_page.route('/<page>')
def show(page):
    try:
        return render_template('pages/%s.html' % page)
    except TemplateNotFound:
        abort(404)

from flask import Flask
from yourapplication.simple_page import simple_page

app = Flask(__name__)
app.register_blueprint(simple_page)

>>> app.url_map
Map([<Rule '/static/<filename>' (HEAD, OPTIONS, GET) -> static>,
 <Rule '/<page>' (HEAD, OPTIONS, GET) -> simple_page.show>,
 <Rule '/' (HEAD, OPTIONS, GET) -> simple_page.show>])

app.register_blueprint(simple_page, url_prefix='/pages')

>>> app.url_map
Map([<Rule '/static/<filename>' (HEAD, OPTIONS, GET) -> static>,
 <Rule '/pages/<page>' (HEAD, OPTIONS, GET) -> simple_page.show>,
 <Rule '/pages/' (HEAD, OPTIONS, GET) -> simple_page.show>])

>>> simple_page.root_path
'/Users/username/TestProject/yourapplication'

with simple_page.open_resource('static/style.css') as f:
    code = f.read()

admin = Blueprint('admin', __name__, static_folder='static')

url_for('admin.static', filename='style.css')

admin = Blueprint('admin', __name__, template_folder='templates')

yourpackage/
    blueprints/
        admin/
            templates/
                admin/
                    index.html
            __init__.py

url_for('admin.index')

url_for('.index')

@simple_page.errorhandler(404)
def page_not_found(e):
    return render_template('pages/404.html')

@app.errorhandler(404)
@app.errorhandler(405)
def _handle_api_error(ex):
    if request.path.startswith('/api/'):
        return jsonify_error(ex)
    else:
        return ex

from flask_foo import Foo

foo = Foo()

app = Flask(__name__)
app.config.update(
    FOO_BAR='baz',
    FOO_SPAM='eggs',
)

foo.init_app(app)

$ export FLASK_APP=hello
$ flask run

> set FLASK_APP=hello
> flask run

> $env:FLASK_APP = "hello"
> flask run

$ flask run
 * Serving Flask app "hello"
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

$ flask shell
Python 3.6.2 (default, Jul 20 2017, 03:52:27)
[GCC 7.1.1 20170630] on linux
App: example
Instance: /home/user/Projects/hello/instance
>>>

$ FLASK_ENV=development flask run
 * Serving Flask app "hello"
 * Environment: development
 * Debug mode: on
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
 * Restarting with inotify reloader
 * Debugger is active!
 * Debugger PIN: 223-456-919

$ flask run --extra-files file1:dirA/file2:dirB/
# or
$ export FLASK_RUN_EXTRA_FILES=file1:dirA/file2:dirB/
$ flask run
 * Running on http://127.0.0.1:8000/
 * Detected change in '/path/to/file1', reloading

$ export FLASK_RUN_PORT=8000
$ flask run
 * Running on http://127.0.0.1:8000/

$ flask run
 * Tip: There are .env files present. Do "pip install python-dotenv" to use them.

$ export FLASK_SKIP_DOTENV=1
$ flask run

$ export FLASK_APP=hello

> set FLASK_APP=hello

import click
from flask import Flask

app = Flask(__name__)

@app.cli.command("create-user")
@click.argument("name")
def create_user(name):
    ...

$ flask create-user admin

import click
from flask import Flask
from flask.cli import AppGroup

app = Flask(__name__)
user_cli = AppGroup('user')

@user_cli.command('create')
@click.argument('name')
def create_user(name):
    ...

app.cli.add_command(user_cli)

$ flask user create demo

from flask import Blueprint

bp = Blueprint('students', __name__)

@bp.cli.command('create')
@click.argument('name')
def create(name):
    ...

app.register_blueprint(bp)

$ flask students create alice

bp = Blueprint('students', __name__, cli_group='other')
# or
app.register_blueprint(bp, cli_group='other')

$ flask other create alice

bp = Blueprint('students', __name__, cli_group=None)
# or
app.register_blueprint(bp, cli_group=None)

$ flask create alice

import click
from flask.cli import with_appcontext

@click.command()
@with_appcontext
def do_work():
    ...

app.cli.add_command(do_work)

@app.cli.command(with_appcontext=False)
def do_work():
    ...

from setuptools import setup

setup(
    name='flask-my-extension',
    ...,
    entry_points={
        'flask.commands': [
            'my-command=flask_my_extension.commands:cli'
        ],
    },
)

import click

@click.command()
def cli():
    ...

import click
from flask import Flask
from flask.cli import FlaskGroup

def create_app():
    app = Flask('wiki')
    # other setup
    return app

@click.group(cls=FlaskGroup, create_app=create_app)
def cli():
    """Management script for the Wiki application."""

from setuptools import setup

setup(
    name='flask-my-extension',
    ...,
    entry_points={
        'console_scripts': [
            'wiki=wiki:cli'
        ],
    },
)

$ pip install -e .
$ wiki run

$ export FLASK_APP=my_application
$ export FLASK_ENV=development
$ flask run

$ flask run --no-reload

if __name__ == '__main__':
    app.run()

>>> ctx = app.test_request_context()

>>> ctx.push()

>>> ctx.pop()

>>> ctx = app.test_request_context()
>>> ctx.push()
>>> app.preprocess_request()

>>> app.process_response(app.response_class())
<Response 0 bytes [200 OK]>
>>> ctx.pop()

>>> from shelltools import *

/yourapplication
    yourapplication.py
    /static
        style.css
    /templates
        layout.html
        index.html
        login.html
        ...

/yourapplication
    /yourapplication
        __init__.py
        /static
            style.css
        /templates
            layout.html
            index.html
            login.html
            ...

from setuptools import setup

setup(
    name='yourapplication',
    packages=['yourapplication'],
    include_package_data=True,
    install_requires=[
        'flask',
    ],
)

$ export FLASK_APP=yourapplication

$ export FLASK_ENV=development

$ pip install -e .
$ flask run

from flask import Flask
app = Flask(__name__)

import yourapplication.views

from yourapplication import app

@app.route('/')
def index():
    return 'Hello World!'

/yourapplication
    setup.py
    /yourapplication
        __init__.py
        views.py
        /static
            style.css
        /templates
            layout.html
            index.html
            login.html
            ...

def create_app(config_filename):
    app = Flask(__name__)
    app.config.from_pyfile(config_filename)

    from yourapplication.model import db
    db.init_app(app)

    from yourapplication.views.admin import admin
    from yourapplication.views.frontend import frontend
    app.register_blueprint(admin)
    app.register_blueprint(frontend)

    return app

from flask import current_app, Blueprint, render_template
admin = Blueprint('admin', __name__, url_prefix='/admin')

@admin.route('/')
def index():
    return render_template(current_app.config['INDEX_TEMPLATE'])

def create_app(config_filename):
    app = Flask(__name__)
    app.config.from_pyfile(config_filename)

    db = SQLAlchemy(app)

db = SQLAlchemy()

def create_app(config_filename):
    app = Flask(__name__)
    app.config.from_pyfile(config_filename)

    from yourapplication.model import db
    db.init_app(app)

$ export FLASK_APP=myapp
$ flask run

$ export FLASK_APP="myapp:create_app('dev')"
$ flask run

from werkzeug.serving import run_simple
run_simple('localhost', 5000, application, use_reloader=True)

from flask import Flask
from werkzeug.serving import run_simple

app = Flask(__name__)
app.debug = True

@app.route('/')
def hello_world():
    return 'Hello World!'

if __name__ == '__main__':
    run_simple('localhost', 5000, app,
               use_reloader=True, use_debugger=True, use_evalex=True)

from werkzeug.middleware.dispatcher import DispatcherMiddleware
from frontend_app import application as frontend
from backend_app import application as backend

application = DispatcherMiddleware(frontend, {
    '/backend': backend
})

from threading import Lock

class SubdomainDispatcher(object):

    def __init__(self, domain, create_app):
        self.domain = domain
        self.create_app = create_app
        self.lock = Lock()
        self.instances = {}

    def get_application(self, host):
        host = host.split(':')[0]
        assert host.endswith(self.domain), 'Configuration error'
        subdomain = host[:-len(self.domain)].rstrip('.')
        with self.lock:
            app = self.instances.get(subdomain)
            if app is None:
                app = self.create_app(subdomain)
                self.instances[subdomain] = app
            return app

    def __call__(self, environ, start_response):
        app = self.get_application(environ['HTTP_HOST'])
        return app(environ, start_response)

from myapplication import create_app, get_user_for_subdomain
from werkzeug.exceptions import NotFound

def make_app(subdomain):
    user = get_user_for_subdomain(subdomain)
    if user is None:
        # if there is no user for that subdomain we still have
        # to return a WSGI application that handles that request.
        # We can then just return the NotFound() exception as
        # application which will render a default 404 page.
        # You might also redirect the user to the main page then
        return NotFound()

    # otherwise create the application for the specific user
    return create_app(user)

application = SubdomainDispatcher('example.com', make_app)

from threading import Lock
from werkzeug.wsgi import pop_path_info, peek_path_info

class PathDispatcher(object):

    def __init__(self, default_app, create_app):
        self.default_app = default_app
        self.create_app = create_app
        self.lock = Lock()
        self.instances = {}

    def get_application(self, prefix):
        with self.lock:
            app = self.instances.get(prefix)
            if app is None:
                app = self.create_app(prefix)
                if app is not None:
                    self.instances[prefix] = app
            return app

    def __call__(self, environ, start_response):
        app = self.get_application(peek_path_info(environ))
        if app is not None:
            pop_path_info(environ)
        else:
            app = self.default_app
        return app(environ, start_response)

from myapplication import create_app, default_app, get_user_for_prefix

def make_app(prefix):
    user = get_user_for_prefix(prefix)
    if user is not None:
        return create_app(user)

application = PathDispatcher(default_app, make_app)

from flask import jsonify

class InvalidUsage(Exception):
    status_code = 400

    def __init__(self, message, status_code=None, payload=None):
        Exception.__init__(self)
        self.message = message
        if status_code is not None:
            self.status_code = status_code
        self.payload = payload

    def to_dict(self):
        rv = dict(self.payload or ())
        rv['message'] = self.message
        return rv

@app.errorhandler(InvalidUsage)
def handle_invalid_usage(error):
    response = jsonify(error.to_dict())
    response.status_code = error.status_code
    return response

@app.route('/foo')
def get_foo():
    raise InvalidUsage('This view is gone', status_code=410)

from flask import Flask, g

app = Flask(__name__)

@app.route('/<lang_code>/')
def index(lang_code):
    g.lang_code = lang_code
    ...

@app.route('/<lang_code>/about')
def about(lang_code):
    g.lang_code = lang_code
    ...

@app.url_defaults
def add_language_code(endpoint, values):
    if 'lang_code' in values or not g.lang_code:
        return
    if app.url_map.is_endpoint_expecting(endpoint, 'lang_code'):
        values['lang_code'] = g.lang_code

@app.url_value_preprocessor
def pull_lang_code(endpoint, values):
    g.lang_code = values.pop('lang_code', None)

from flask import Flask, g

app = Flask(__name__)

@app.url_defaults
def add_language_code(endpoint, values):
    if 'lang_code' in values or not g.lang_code:
        return
    if app.url_map.is_endpoint_expecting(endpoint, 'lang_code'):
        values['lang_code'] = g.lang_code

@app.url_value_preprocessor
def pull_lang_code(endpoint, values):
    g.lang_code = values.pop('lang_code', None)

@app.route('/<lang_code>/')
def index():
    ...

@app.route('/<lang_code>/about')
def about():
    ...

from flask import Blueprint, g

bp = Blueprint('frontend', __name__, url_prefix='/<lang_code>')

@bp.url_defaults
def add_language_code(endpoint, values):
    values.setdefault('lang_code', g.lang_code)

@bp.url_value_preprocessor
def pull_lang_code(endpoint, values):
    g.lang_code = values.pop('lang_code')

@bp.route('/')
def index():
    ...

@bp.route('/about')
def about():
    ...

from setuptools import setup

setup(
    name='Your Application',
    version='1.0',
    long_description=__doc__,
    packages=['yourapplication'],
    include_package_data=True,
    zip_safe=False,
    install_requires=['Flask']
)

from setuptools import setup, find_packages

setup(
    ...
    packages=find_packages()
)

[egg_info]
tag_build = .dev
tag_date = 1

[aliases]
release = egg_info -Db ''

recursive-include yourapplication/templates *
recursive-include yourapplication/static *

install_requires=[
    'Flask>=0.2',
    'SQLAlchemy>=0.6',
    'BrokenPackage>=0.7,<=1.0'
]

dependency_links=['http://example.com/yourfiles']

$ python setup.py install

$ python setup.py develop

from fabric.api import *

# the user to use for the remote commands
env.user = 'appuser'
# the servers where the commands are executed
env.hosts = ['server1.example.com', 'server2.example.com']

def pack():
    # build the package
    local('python setup.py sdist --formats=gztar', capture=False)

def deploy():
    # figure out the package name and version
    dist = local('python setup.py --fullname', capture=True).strip()
    filename = '%s.tar.gz' % dist

    # upload the package to the temporary folder on the server
    put('dist/%s' % filename, '/tmp/%s' % filename)

    # install the package in the application's virtualenv with pip
    run('/var/www/yourapplication/env/bin/pip install /tmp/%s' % filename)

    # remove the uploaded package
    run('rm -r /tmp/%s' % filename)

    # touch the .wsgi file to trigger a reload in mod_wsgi
    run('touch /var/www/yourapplication.wsgi')

$ fab pack deploy

$ fab -H newserver.example.com bootstrap

$ mkdir /var/www/yourapplication
$ cd /var/www/yourapplication
$ virtualenv --distribute env

import os
os.environ['YOURAPPLICATION_CONFIG'] = '/var/www/yourapplication/application.cfg'
from yourapplication import app

app = Flask(__name__)
app.config.from_object('yourapplication.default_config')
app.config.from_envvar('YOURAPPLICATION_CONFIG')

$ fab pack deploy

import sqlite3
from flask import g

DATABASE = '/path/to/database.db'

def get_db():
    db = getattr(g, '_database', None)
    if db is None:
        db = g._database = sqlite3.connect(DATABASE)
    return db

@app.teardown_appcontext
def close_connection(exception):
    db = getattr(g, '_database', None)
    if db is not None:
        db.close()

@app.route('/')
def index():
    cur = get_db().cursor()
    ...

with app.app_context():
    # now you can use get_db()

def make_dicts(cursor, row):
    return dict((cursor.description[idx][0], value)
                for idx, value in enumerate(row))

db.row_factory = make_dicts

db.row_factory = sqlite3.Row

>>> # You can get values based on the row's name
>>> r['FirstName']
John
>>> # Or, you can get them based on index
>>> r[1]
John
# Row objects are also iterable:
>>> for value in r:
...     print(value)
1
John
Doe
M

def query_db(query, args=(), one=False):
    cur = get_db().execute(query, args)
    rv = cur.fetchall()
    cur.close()
    return (rv[0] if rv else None) if one else rv

for user in query_db('select * from users'):
    print user['username'], 'has the id', user['user_id']

user = query_db('select * from users where username = ?',
                [the_username], one=True)
if user is None:
    print 'No such user'
else:
    print the_username, 'has the id', user['user_id']

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()

>>> from yourapplication import init_db
>>> init_db()

from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session, sessionmaker
from sqlalchemy.ext.declarative import declarative_base

engine = create_engine('sqlite:////tmp/test.db', convert_unicode=True)
db_session = scoped_session(sessionmaker(autocommit=False,
                                         autoflush=False,
                                         bind=engine))
Base = declarative_base()
Base.query = db_session.query_property()

def init_db():
    # import all modules here that might define models so that
    # they will be registered properly on the metadata.  Otherwise
    # you will have to import them first before calling init_db()
    import yourapplication.models
    Base.metadata.create_all(bind=engine)

from yourapplication.database import db_session

@app.teardown_appcontext
def shutdown_session(exception=None):
    db_session.remove()

from sqlalchemy import Column, Integer, String
from yourapplication.database import Base

class User(Base):
    __tablename__ = 'users'
    id = Column(Integer, primary_key=True)
    name = Column(String(50), unique=True)
    email = Column(String(120), unique=True)

    def __init__(self, name=None, email=None):
        self.name = name
        self.email = email

    def __repr__(self):
        return '<User %r>' % (self.name)

>>> from yourapplication.database import init_db
>>> init_db()

>>> from yourapplication.database import db_session
>>> from yourapplication.models import User
>>> u = User('admin', 'admin@localhost')
>>> db_session.add(u)
>>> db_session.commit()

>>> User.query.all()
[<User u'admin'>]
>>> User.query.filter(User.name == 'admin').first()
<User u'admin'>

from sqlalchemy import create_engine, MetaData
from sqlalchemy.orm import scoped_session, sessionmaker

engine = create_engine('sqlite:////tmp/test.db', convert_unicode=True)
metadata = MetaData()
db_session = scoped_session(sessionmaker(autocommit=False,
                                         autoflush=False,
                                         bind=engine))
def init_db():
    metadata.create_all(bind=engine)

from yourapplication.database import db_session

@app.teardown_appcontext
def shutdown_session(exception=None):
    db_session.remove()

from sqlalchemy import Table, Column, Integer, String
from sqlalchemy.orm import mapper
from yourapplication.database import metadata, db_session

class User(object):
    query = db_session.query_property()

    def __init__(self, name=None, email=None):
        self.name = name
        self.email = email

    def __repr__(self):
        return '<User %r>' % (self.name)

users = Table('users', metadata,
    Column('id', Integer, primary_key=True),
    Column('name', String(50), unique=True),
    Column('email', String(120), unique=True)
)
mapper(User, users)

from sqlalchemy import create_engine, MetaData, Table

engine = create_engine('sqlite:////tmp/test.db', convert_unicode=True)
metadata = MetaData(bind=engine)

from sqlalchemy import Table

users = Table('users', metadata, autoload=True)

>>> con = engine.connect()
>>> con.execute(users.insert(), name='admin', email='admin@localhost')

>>> users.select(users.c.id == 1).execute().first()
(1, u'admin', u'admin@localhost')

>>> r = users.select(users.c.id == 1).execute().first()
>>> r['name']
u'admin'

>>> engine.execute('select * from users where id = :1', [1]).first()
(1, u'admin', u'admin@localhost')

import os
from flask import Flask, flash, request, redirect, url_for
from werkzeug.utils import secure_filename

UPLOAD_FOLDER = '/path/to/the/uploads'
ALLOWED_EXTENSIONS = {'txt', 'pdf', 'png', 'jpg', 'jpeg', 'gif'}

app = Flask(__name__)
app.config['UPLOAD_FOLDER'] = UPLOAD_FOLDER

def allowed_file(filename):
    return '.' in filename and \
           filename.rsplit('.', 1)[1].lower() in ALLOWED_EXTENSIONS

@app.route('/', methods=['GET', 'POST'])
def upload_file():
    if request.method == 'POST':
        # check if the post request has the file part
        if 'file' not in request.files:
            flash('No file part')
            return redirect(request.url)
        file = request.files['file']
        # if user does not select file, browser also
        # submit an empty part without filename
        if file.filename == '':
            flash('No selected file')
            return redirect(request.url)
        if file and allowed_file(file.filename):
            filename = secure_filename(file.filename)
            file.save(os.path.join(app.config['UPLOAD_FOLDER'], filename))
            return redirect(url_for('uploaded_file',
                                    filename=filename))
    return '''
    <!doctype html>
    <title>Upload new File</title>
    <h1>Upload new File</h1>
    <form method=post enctype=multipart/form-data>
      <input type=file name=file>
      <input type=submit value=Upload>
    </form>
    '''

filename = "../../../../home/username/.bashrc"

>>> secure_filename('../../../../home/username/.bashrc')
'home_username_.bashrc'

from flask import send_from_directory

@app.route('/uploads/<filename>')
def uploaded_file(filename):
    return send_from_directory(app.config['UPLOAD_FOLDER'],
                               filename)

from werkzeug.middleware.shared_data import SharedDataMiddleware
app.add_url_rule('/uploads/<filename>', 'uploaded_file',
                 build_only=True)
app.wsgi_app = SharedDataMiddleware(app.wsgi_app, {
    '/uploads':  app.config['UPLOAD_FOLDER']
})

from flask import Flask, Request

app = Flask(__name__)
app.config['MAX_CONTENT_LENGTH'] = 16 * 1024 * 1024

from functools import wraps
from flask import g, request, redirect, url_for

def login_required(f):
    @wraps(f)
    def decorated_function(*args, **kwargs):
        if g.user is None:
            return redirect(url_for('login', next=request.url))
        return f(*args, **kwargs)
    return decorated_function

@app.route('/secret_page')
@login_required
def secret_page():
    pass

<input type="hidden" value="{{ request.args.get('next', '') }}"/>

from functools import wraps
from flask import request

def cached(timeout=5 * 60, key='view/%s'):
    def decorator(f):
        @wraps(f)
        def decorated_function(*args, **kwargs):
            cache_key = key % request.path
            rv = cache.get(cache_key)
            if rv is not None:
                return rv
            rv = f(*args, **kwargs)
            cache.set(cache_key, rv, timeout=timeout)
            return rv
        return decorated_function
    return decorator

@app.route('/')
def index():
    return render_template('index.html', value=42)

@app.route('/')
@templated('index.html')
def index():
    return dict(value=42)

@app.route('/')
@templated()
def index():
    return dict(value=42)

from functools import wraps
from flask import request, render_template

def templated(template=None):
    def decorator(f):
        @wraps(f)
        def decorated_function(*args, **kwargs):
            template_name = template
            if template_name is None:
                template_name = request.endpoint \
                    .replace('.', '/') + '.html'
            ctx = f(*args, **kwargs)
            if ctx is None:
                ctx = {}
            elif not isinstance(ctx, dict):
                return ctx
            return render_template(template_name, **ctx)
        return decorated_function
    return decorator

from flask import Flask
from werkzeug.routing import Rule

app = Flask(__name__)
app.url_map.add(Rule('/', endpoint='index'))

@app.endpoint('index')
def my_index():
    return "Hello world"

from wtforms import Form, BooleanField, StringField, PasswordField, validators

class RegistrationForm(Form):
    username = StringField('Username', [validators.Length(min=4, max=25)])
    email = StringField('Email Address', [validators.Length(min=6, max=35)])
    password = PasswordField('New Password', [
        validators.DataRequired(),
        validators.EqualTo('confirm', message='Passwords must match')
    ])
    confirm = PasswordField('Repeat Password')
    accept_tos = BooleanField('I accept the TOS', [validators.DataRequired()])

@app.route('/register', methods=['GET', 'POST'])
def register():
    form = RegistrationForm(request.form)
    if request.method == 'POST' and form.validate():
        user = User(form.username.data, form.email.data,
                    form.password.data)
        db_session.add(user)
        flash('Thanks for registering')
        return redirect(url_for('login'))
    return render_template('register.html', form=form)

{% macro render_field(field) %}
  <dt>{{ field.label }}
  <dd>{{ field(**kwargs)|safe }}
  {% if field.errors %}
    <ul class=errors>
    {% for error in field.errors %}
      <li>{{ error }}</li>
    {% endfor %}
    </ul>
  {% endif %}
  </dd>
{% endmacro %}

{% from "_formhelpers.html" import render_field %}
<form method=post>
  <dl>
    {{ render_field(form.username) }}
    {{ render_field(form.email) }}
    {{ render_field(form.password) }}
    {{ render_field(form.confirm) }}
    {{ render_field(form.accept_tos) }}
  </dl>
  <p><input type=submit value=Register>
</form>

<!doctype html>
<html>
  <head>
    {% block head %}
    <link rel="stylesheet" href="{{ url_for('static', filename='style.css') }}">
    <title>{% block title %}{% endblock %} - My Webpage</title>
    {% endblock %}
  </head>
  <body>
    <div id="content">{% block content %}{% endblock %}</div>
    <div id="footer">
      {% block footer %}
      &copy; Copyright 2010 by <a href="http://domain.invalid/">you</a>.
      {% endblock %}
    </div>
  </body>
</html>

{% extends "layout.html" %}
{% block title %}Index{% endblock %}
{% block head %}
  {{ super() }}
  <style type="text/css">
    .important { color: #336699; }
  </style>
{% endblock %}
{% block content %}
  <h1>Index</h1>
  <p class="important">
    Welcome on my awesome homepage.
{% endblock %}

from flask import Flask, flash, redirect, render_template, \
     request, url_for

app = Flask(__name__)
app.secret_key = b'_5#y2L"F4Q8z\n\xec]/'

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

@app.route('/login', methods=['GET', 'POST'])
def login():
    error = None
    if request.method == 'POST':
        if request.form['username'] != 'admin' or \
                request.form['password'] != 'secret':
            error = 'Invalid credentials'
        else:
            flash('You were successfully logged in')
            return redirect(url_for('index'))
    return render_template('login.html', error=error)

<!doctype html>
<title>My Application</title>
{% with messages = get_flashed_messages() %}
  {% if messages %}
    <ul class=flashes>
    {% for message in messages %}
      <li>{{ message }}</li>
    {% endfor %}
    </ul>
  {% endif %}
{% endwith %}
{% block body %}{% endblock %}

{% extends "layout.html" %}
{% block body %}
  <h1>Overview</h1>
  <p>Do you want to <a href="{{ url_for('login') }}">log in?</a>
{% endblock %}

{% extends "layout.html" %}
{% block body %}
  <h1>Login</h1>
  {% if error %}
    <p class=error><strong>Error:</strong> {{ error }}
  {% endif %}
  <form method=post>
    <dl>
      <dt>Username:
      <dd><input type=text name=username value="{{
          request.form.username }}">
      <dt>Password:
      <dd><input type=password name=password>
    </dl>
    <p><input type=submit value=Login>
  </form>
{% endblock %}

flash(u'Invalid password provided', 'error')

{% with messages = get_flashed_messages(with_categories=true) %}
  {% if messages %}
    <ul class=flashes>
    {% for category, message in messages %}
      <li class="{{ category }}">{{ message }}</li>
    {% endfor %}
    </ul>
  {% endif %}
{% endwith %}

{% with errors = get_flashed_messages(category_filter=["error"]) %}
{% if errors %}
<div class="alert-message block-message error">
  <a class="close" href="#">×</a>
  <ul>
    {%- for msg in errors %}
    <li>{{ msg }}</li>
    {% endfor -%}
  </ul>
</div>
{% endif %}
{% endwith %}

<script type=text/javascript src="{{
  url_for('static', filename='jquery.js') }}"></script>

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="{{
  url_for('static', filename='jquery.js') }}">\x3C/script>')</script>

<script type=text/javascript>
  $SCRIPT_ROOT = {{ request.script_root|tojson|safe }};
</script>

from flask import Flask, jsonify, render_template, request
app = Flask(__name__)

@app.route('/_add_numbers')
def add_numbers():
    a = request.args.get('a', 0, type=int)
    b = request.args.get('b', 0, type=int)
    return jsonify(result=a + b)

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

<script type=text/javascript>
  $(function() {
    $('a#calculate').bind('click', function() {
      $.getJSON($SCRIPT_ROOT + '/_add_numbers', {
        a: $('input[name="a"]').val(),
        b: $('input[name="b"]').val()
      }, function(data) {
        $("#result").text(data.result);
      });
      return false;
    });
  });
</script>
<h1>jQuery Example</h1>
<p><input type=text size=5 name=a> +
   <input type=text size=5 name=b> =
   <span id=result>?</span>
<p><a href=# id=calculate>calculate server side</a>

from flask import render_template

@app.errorhandler(404)
def page_not_found(e):
    # note that we set the 404 status explicitly
    return render_template('404.html'), 404

from flask import Flask, render_template

def page_not_found(e):
  return render_template('404.html'), 404

def create_app(config_filename):
    app = Flask(__name__)
    app.register_error_handler(404, page_not_found)
    return app

{% extends "layout.html" %}
{% block title %}Page Not Found{% endblock %}
{% block body %}
  <h1>Page Not Found</h1>
  <p>What you were looking for is just not there.
  <p><a href="{{ url_for('index') }}">go somewhere nice</a>
{% endblock %}

from flask import abort, jsonify

@app.errorhandler(404)
def resource_not_found(e):
    return jsonify(error=str(e)), 404

@app.route("/cheese")
def get_one_cheese():
    resource = get_resource()

    if resource is None:
        abort(404, description="Resource not found")

    return jsonify(resource)

from flask import Flask
app = Flask(__name__)

@app.route('/')
def index():
    pass

@app.route('/user/<username>')
def user(username):
    pass

def index():
    pass

def user(username):
    pass

from flask import Flask
from yourapplication import views
app = Flask(__name__)
app.add_url_rule('/', view_func=views.index)
app.add_url_rule('/user/<username>', view_func=views.user)

from werkzeug.utils import import_string, cached_property

class LazyView(object):

    def __init__(self, import_name):
        self.__module__, self.__name__ = import_name.rsplit('.', 1)
        self.import_name = import_name

    @cached_property
    def view(self):
        return import_string(self.import_name)

    def __call__(self, *args, **kwargs):
        return self.view(*args, **kwargs)

from flask import Flask
from yourapplication.helpers import LazyView
app = Flask(__name__)
app.add_url_rule('/',
                 view_func=LazyView('yourapplication.views.index'))
app.add_url_rule('/user/<username>',
                 view_func=LazyView('yourapplication.views.user'))

def url(import_name, url_rules=[], **options):
    view = LazyView('yourapplication.' + import_name)
    for url_rule in url_rules:
        app.add_url_rule(url_rule, view_func=view, **options)

# add a single route to the index view
url('views.index', ['/'])

# add two routes to a single function endpoint
url_rules = ['/user/','/user/<username>']
url('views.user', url_rules)

pip install flask-mongoengine

from flask import Flask
from flask_mongoengine import MongoEngine

app = Flask(__name__)
app.config['MONGODB_SETTINGS'] = {
    "db": "myapp",
}
db = MongoEngine(app)

import mongoengine as me

class Movie(me.Document):
    title = me.StringField(required=True)
    year = me.IntField()
    rated = me.StringField()
    director = me.StringField()
    actors = me.ListField()

class Imdb(me.EmbeddedDocument):
    imdb_id = me.StringField()
    rating = me.DecimalField()
    votes = me.IntField()

class Movie(me.Document):
    ...
    imdb = me.EmbeddedDocumentField(Imdb)

bttf = Movie(title="Back To The Future", year=1985)
bttf.actors = [
    "Michael J. Fox",
    "Christopher Lloyd"
]
bttf.imdb = Imdb(imdb_id="tt0088763", rating=8.5)
bttf.save()

bttf = Movies.objects(title="Back To The Future").get_or_404()

some_theron_movie = Movie.objects(actors__in=["Charlize Theron"]).first()

for recents in Movie.objects(year__gte=2017):
    print(recents.title)

<link rel="shortcut icon" href="{{ url_for('static', filename='favicon.ico') }}">

app.add_url_rule('/favicon.ico',
                 redirect_to=url_for('static', filename='favicon.ico'))

import os
from flask import send_from_directory

@app.route('/favicon.ico')
def favicon():
    return send_from_directory(os.path.join(app.root_path, 'static'),
                               'favicon.ico', mimetype='image/vnd.microsoft.icon')

from flask import Response

@app.route('/large.csv')
def generate_large_csv():
    def generate():
        for row in iter_all_rows():
            yield ','.join(row) + '\n'
    return Response(generate(), mimetype='text/csv')

from flask import Response

def stream_template(template_name, **context):
    app.update_template_context(context)
    t = app.jinja_env.get_template(template_name)
    rv = t.stream(context)
    rv.enable_buffering(5)
    return rv

@app.route('/my-large-page.html')
def render_large_template():
    rows = iter_all_rows()
    return Response(stream_template('the_template.html', rows=rows))

from flask import stream_with_context, request, Response

@app.route('/stream')
def streamed_response():
    def generate():
        yield 'Hello '
        yield request.args['name']
        yield '!'
    return Response(stream_with_context(generate()))

from flask import request, after_this_request

@app.before_request
def detect_user_language():
    language = request.cookies.get('user_lang')

    if language is None:
        language = guess_language_from_request()

        # when the response exists, set a cookie with the language
        @after_this_request
        def remember_language(response):
            response.set_cookie('user_lang', language)
            return response

    g.language = language

class HTTPMethodOverrideMiddleware(object):
    allowed_methods = frozenset([
        'GET',
        'HEAD',
        'POST',
        'DELETE',
        'PUT',
        'PATCH',
        'OPTIONS'
    ])
    bodyless_methods = frozenset(['GET', 'HEAD', 'OPTIONS', 'DELETE'])

    def __init__(self, app):
        self.app = app

    def __call__(self, environ, start_response):
        method = environ.get('HTTP_X_HTTP_METHOD_OVERRIDE', '').upper()
        if method in self.allowed_methods:
            environ['REQUEST_METHOD'] = method
        if method in self.bodyless_methods:
            environ['CONTENT_LENGTH'] = '0'
        return self.app(environ, start_response)

from flask import Flask

app = Flask(__name__)
app.wsgi_app = HTTPMethodOverrideMiddleware(app.wsgi_app)

import hashlib

class ChecksumCalcStream(object):

    def __init__(self, stream):
        self._stream = stream
        self._hash = hashlib.sha1()

    def read(self, bytes):
        rv = self._stream.read(bytes)
        self._hash.update(rv)
        return rv

    def readline(self, size_hint):
        rv = self._stream.readline(size_hint)
        self._hash.update(rv)
        return rv

def generate_checksum(request):
    env = request.environ
    stream = ChecksumCalcStream(env['wsgi.input'])
    env['wsgi.input'] = stream
    return stream._hash

@app.route('/special-api', methods=['POST'])
def special_api():
    hash = generate_checksum(request)
    # Accessing this parses the input stream
    files = request.files
    # At this point the hash is fully constructed.
    checksum = hash.hexdigest()
    return 'Hash was: %s' % checksum

$ pip install celery

from celery import Celery

def make_celery(app):
    celery = Celery(
        app.import_name,
        backend=app.config['CELERY_RESULT_BACKEND'],
        broker=app.config['CELERY_BROKER_URL']
    )
    celery.conf.update(app.config)

    class ContextTask(celery.Task):
        def __call__(self, *args, **kwargs):
            with app.app_context():
                return self.run(*args, **kwargs)

    celery.Task = ContextTask
    return celery

from flask import Flask

flask_app = Flask(__name__)
flask_app.config.update(
    CELERY_BROKER_URL='redis://localhost:6379',
    CELERY_RESULT_BACKEND='redis://localhost:6379'
)
celery = make_celery(flask_app)

@celery.task()
def add_together(a, b):
    return a + b

result = add_together.delay(23, 42)
result.wait()  # 65

$ celery -A your_application.celery worker

from flask import Flask, Request
from werkzeug.datastructures import ImmutableOrderedMultiDict
class MyRequest(Request):
    """Request subclass to override request parameter storage"""
    parameter_storage_class = ImmutableOrderedMultiDict
class MyFlask(Flask):
    """Flask subclass using the custom request class"""
    request_class = MyRequest

from flask import Flask, jsonify

app = Flask(__name__, static_folder='app', static_url_path="/app")

@app.route("/heartbeat")
def heartbeat():
    return jsonify({"status": "healthy"})

@app.route('/', defaults={'path': ''})
@app.route('/<path:path>')
def catch_all(path):
    return app.send_static_file("index.html")

$ gunicorn myproject:app

$ gunicorn -w 4 -b 127.0.0.1:4000 myproject:app

$ gunicorn "myproject:create_app()"

$ uwsgi --http 127.0.0.1:5000 --module myproject:app

from gevent.pywsgi import WSGIServer
from yourapplication import app

http_server = WSGIServer(('', 5000), app)
http_server.serve_forever()

$ twistd web --wsgi myproject.app

$ twistd -n web --port tcp:8080 --wsgi myproject.app

server {
    listen 80;

    server_name _;

    access_log  /var/log/nginx/access.log;
    error_log  /var/log/nginx/error.log;

    location / {
        proxy_pass         http://127.0.0.1:8000/;
        proxy_redirect     off;

        proxy_set_header   Host                 $host;
        proxy_set_header   X-Real-IP            $remote_addr;
        proxy_set_header   X-Forwarded-For      $proxy_add_x_forwarded_for;
        proxy_set_header   X-Forwarded-Proto    $scheme;
    }
}

from werkzeug.middleware.proxy_fix import ProxyFix
app.wsgi_app = ProxyFix(app.wsgi_app, x_proto=1, x_host=1)

class CustomProxyFix(object):

    def __init__(self, app):
        self.app = app

    def __call__(self, environ, start_response):
        host = environ.get('HTTP_X_FHOST', '')
        if host:
            environ['HTTP_HOST'] = host
        return self.app(environ, start_response)

app.wsgi_app = CustomProxyFix(app.wsgi_app)

$ uwsgi -s /tmp/yourapplication.sock --manage-script-name --mount /yourapplication=myapp:app

location = /yourapplication { rewrite ^ /yourapplication/; }
location /yourapplication { try_files $uri @yourapplication; }
location @yourapplication {
  include uwsgi_params;
  uwsgi_pass unix:/tmp/yourapplication.sock;
}

location / { try_files $uri @yourapplication; }
location @yourapplication {
    include uwsgi_params;
    uwsgi_pass unix:/tmp/yourapplication.sock;
}

$ apt-get install libapache2-mod-wsgi-py3

$ yum install mod_wsgi

$ pkg install ap24-py37-mod_wsgi

from yourapplication import app as application

from yourapplication import create_app
application = create_app()

import sys
sys.path.insert(0, '/path/to/the/application')

<VirtualHost *>
    ServerName example.com

    WSGIDaemonProcess yourapplication user=user1 group=group1 threads=5
    WSGIScriptAlias / /var/www/yourapplication/yourapplication.wsgi

    <Directory /var/www/yourapplication>
        WSGIProcessGroup yourapplication
        WSGIApplicationGroup %{GLOBAL}
        Order deny,allow
        Allow from all
    </Directory>
</VirtualHost>

<VirtualHost *>
    ServerName example.com
    WSGIScriptAlias / C:\yourdir\yourapp.wsgi
    <Directory C:\yourdir>
        Order deny,allow
        Allow from all
    </Directory>
</VirtualHost>

Order allow,deny
Allow from all

Require all granted

WSGIRestrictStdout Off

import sys
sys.stdout = sys.stderr

WSGIScriptReloading On

activate_this = '/path/to/env/bin/activate_this.py'
execfile(activate_this, dict(__file__=activate_this))

activate_this = '/path/to/env/bin/activate_this.py'
with open(activate_this) as file_:
    exec(file_.read(), dict(__file__=activate_this))

#!/usr/bin/python
from flup.server.fcgi import WSGIServer
from yourapplication import app

if __name__ == '__main__':
    WSGIServer(app).run()

WSGIServer(application, bindAddress='/path/to/fcgi.sock').run()

$ chmod +x /var/www/yourapplication/yourapplication.fcgi

LoadModule fastcgi_module /usr/lib64/httpd/modules/mod_fastcgi.so

FastCgiServer /var/www/html/yourapplication/app.fcgi -idle-timeout 300 -processes 5

<VirtualHost *>
    ServerName webapp1.mydomain.com
    DocumentRoot /var/www/html/yourapplication

    AddHandler fastcgi-script fcgi
    ScriptAlias / /var/www/html/yourapplication/app.fcgi/

    <Location />
        SetHandler fastcgi-script
    </Location>
</VirtualHost>

FastCgiServer /var/www/html/yourapplication -host 127.0.0.1:3000

<IfModule mod_fcgid.c>
   AddHandler fcgid-script .fcgi
   <Files ~ (\.fcgi)>
       SetHandler fcgid-script
       Options +FollowSymLinks +ExecCGI
   </Files>
</IfModule>

<IfModule mod_rewrite.c>
   Options +FollowSymlinks
   RewriteEngine On
   RewriteBase /
   RewriteCond %{REQUEST_FILENAME} !-f
   RewriteRule ^(.*)$ yourapplication.fcgi/$1 [QSA,L]
</IfModule>

#!/usr/bin/python
#: optional path to your local python site-packages folder
import sys
sys.path.insert(0, '<your_local_path>/lib/python<your_python_version>/site-packages')

from flup.server.fcgi import WSGIServer
from yourapplication import app

class ScriptNameStripper(object):
   def __init__(self, app):
       self.app = app

   def __call__(self, environ, start_response):
       environ['SCRIPT_NAME'] = ''
       return self.app(environ, start_response)

app = ScriptNameStripper(app)

if __name__ == '__main__':
    WSGIServer(app).run()

fastcgi.server = ("/yourapplication.fcgi" =>
    ((
        "socket" => "/tmp/yourapplication-fcgi.sock",
        "bin-path" => "/var/www/yourapplication/yourapplication.fcgi",
        "check-local" => "disable",
        "max-procs" => 1
    ))
)

alias.url = (
    "/static/" => "/path/to/your/static/"
)

url.rewrite-once = (
    "^(/static($|/.*))$" => "$1",
    "^(/.*)$" => "/yourapplication.fcgi$1"
)

location = /yourapplication { rewrite ^ /yourapplication/ last; }
location /yourapplication { try_files $uri @yourapplication; }
location @yourapplication {
    include fastcgi_params;
    fastcgi_split_path_info ^(/yourapplication)(.*)$;
    fastcgi_param PATH_INFO $fastcgi_path_info;
    fastcgi_param SCRIPT_NAME $fastcgi_script_name;
    fastcgi_pass unix:/tmp/yourapplication-fcgi.sock;
}

location / { try_files $uri @yourapplication; }
location @yourapplication {
    include fastcgi_params;
    fastcgi_param PATH_INFO $fastcgi_script_name;
    fastcgi_param SCRIPT_NAME "";
    fastcgi_pass unix:/tmp/yourapplication-fcgi.sock;
}

$ screen
$ /var/www/yourapplication/yourapplication.fcgi

$ su www-data
$ cd /var/www/yourapplication
$ python application.fcgi
Traceback (most recent call last):
  File "yourapplication.fcgi", line 4, in <module>
ImportError: No module named yourapplication

#!/usr/bin/python
from wsgiref.handlers import CGIHandler
from yourapplication import app

CGIHandler().run(app)

ScriptAlias /app /path/to/the/application.cgi

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f # Don't interfere with static files
RewriteRule ^(.*)$ /path/to/the/application.cgi/$1 [L]

from flask import Flask
app = Flask(__name__)

app = Flask('yourapplication')
app = Flask(__name__.split('.')[0])

@app.route('/')
def index():
    pass

def index():
    pass
app.add_url_rule('/', 'index', index)

app.view_functions['index'] = index

with app.app_context():
    init_db()

@app.endpoint('example.endpoint')
def example():
    return "example"

@app.errorhandler(404)
def page_not_found(error):
    return 'This page does not exist', 404

@app.errorhandler(DatabaseError)
def special_exception_handler(error):
    return 'Database connection failed', 500

if not hasattr(app, 'extensions'):
    app.extensions = {}
app.extensions['extensionname'] = SomeObject()

class MyFlask(flask.Flask):
    def get_send_file_max_age(self, name):
        if name.lower().endswith('.js'):
            return 60
        return flask.Flask.get_send_file_max_age(self, name)

/myapplication.py
/schema.sql
/static
    /style.css
/templates
    /layout.html
    /index.html

with app.open_resource('schema.sql') as f:
    contents = f.read()
    do_something_with(contents)

@app.route('/')
def index():
    return 'Hello World'

ctx = app.app_context()
ctx.push()
...
ctx.pop()

ctx = app.test_request_context()
ctx.push()
...
ctx.pop()

@app.template_filter()
def reverse(s):
    return s[::-1]

@app.template_global()
def double(n):
    return 2 * n

@app.template_test()
def is_prime(n):
    if n == 2:
        return True
    for i in range(2, int(math.ceil(math.sqrt(n))) + 1):
        if n % i == 0:
            return False
    return True

app.testing = True
client = app.test_client()

with app.test_client() as c:
    rv = c.get('/?vodka=42')
    assert request.args['vodka'] == '42'

from flask.testing import FlaskClient

class CustomClient(FlaskClient):
    def __init__(self, *args, **kwargs):
        self._authentication = kwargs.pop("authentication")
        super(CustomClient,self).__init__( *args, **kwargs)

app.test_client_class = CustomClient
client = app.test_client(authentication='Basic ....')

with test_request_context(...):
    generate_report()

ctx = app.test_request_context(...)
ctx.push()
...
ctx.pop()

from werkzeug.routing import BaseConverter

class ListConverter(BaseConverter):
    def to_python(self, value):
        return value.split(',')
    def to_url(self, values):
        return ','.join(super(ListConverter, self).to_url(value)
                        for value in values)

app = Flask(__name__)
app.url_map.converters['list'] = ListConverter

app = MyMiddleware(app)

app.wsgi_app = MyMiddleware(app.wsgi_app)

class MyFlask(flask.Flask):
    def get_send_file_max_age(self, name):
        if name.lower().endswith('.js'):
            return 60
        return flask.Flask.get_send_file_max_age(self, name)

/myapplication.py
/schema.sql
/static
    /style.css
/templates
    /layout.html
    /index.html

with app.open_resource('schema.sql') as f:
    contents = f.read()
    do_something_with(contents)

http://www.example.com/myapplication

http://www.example.com/myapplication/%CF%80/page.html?x=y

@Request.application
def my_wsgi_app(request):
    return Response('Hello World!')

# this change is not picked up because a mutable object (here
# a list) is changed.
session['objects'].append(42)
# so mark it as modified yourself
session.modified = True

class Session(dict, SessionMixin):
    pass

app = Flask(__name__)
app.session_interface = MySessionInterface()

with client.session_transaction() as session:
    session['value'] = 42

class User(db.Model):

    def __init__(self, username, remote_addr=None):
        self.username = username
        if remote_addr is None and has_request_context():
            remote_addr = request.remote_addr
        self.remote_addr = remote_addr

class User(db.Model):

    def __init__(self, username, remote_addr=None):
        self.username = username
        if remote_addr is None and request:
            remote_addr = request.remote_addr
        self.remote_addr = remote_addr

import gevent
from flask import copy_current_request_context

@app.route('/')
def index():
    @copy_current_request_context
    def do_some_work():
        # do some work here, it can access flask.request or
        # flask.session like you would otherwise in the view function.
        ...
    gevent.spawn(do_some_work)
    return 'Regular response'

url_for('.index')

def external_url_handler(error, endpoint, values):
    "Looks up an external URL when `url_for` cannot build a URL."
    # This is an example of hooking the build_error_handler.
    # Here, lookup_url is some utility function you've built
    # which looks up the endpoint in some external URL registry.
    url = lookup_url(endpoint, **values)
    if url is None:
        # External lookup did not have a URL.
        # Re-raise the BuildError, in context of original traceback.
        exc_type, exc_value, tb = sys.exc_info()
        if exc_value is error:
            raise exc_type, exc_value, tb
        else:
            raise error
    # url_for will use this result, instead of raising BuildError.
    return url

app.url_build_error_handlers.append(external_url_handler)

abort(404)  # 404 Not Found
abort(Response('Hello World'))

def index():
    return render_template('index.html', foo=42)

def index():
    response = make_response(render_template('index.html', foo=42))
    response.headers['X-Parachutes'] = 'parachutes are cool'
    return response

response = make_response(render_template('not_found.html'), 404)

response = make_response(view_function())
response.headers['X-Parachutes'] = 'parachutes are cool'

@app.route('/')
def index():
    @after_this_request
    def add_header(response):
        response.headers['X-Foo'] = 'Parachute'
        return response
    return 'Hello World!'

@app.route('/uploads/<path:filename>')
def download_file(filename):
    return send_from_directory(app.config['UPLOAD_FOLDER'],
                               filename, as_attachment=True)

@app.route('/wiki/<path:filename>')
def wiki_page(filename):
    filename = safe_join(app.config['WIKI_FOLDER'], filename)
    with open(filename, 'rb') as fd:
        content = fd.read()  # Read and process the file content...

>>> Markup("Main &raquo;        <em>About</em>").striptags()
'Main » About'

>>> Markup("Main &raquo; <em>About</em>").unescape()
'Main » <em>About</em>'

try:
    import simplejson as json
except ImportError:
    import json

from flask import json

<script type=text/javascript>
    doSomethingWith({{ user.username|tojson|safe }});
</script>

from flask import jsonify

@app.route('/_get_current_user')
def get_current_user():
    return jsonify(username=g.user.username,
                   email=g.user.email,
                   id=g.user.id)

{
    "username": "admin",
    "email": "admin@localhost",
    "id": 42
}

def default(self, o):
    try:
        iterable = iter(o)
    except TypeError:
        pass
    else:
        return list(iterable)
    return JSONEncoder.default(self, o)

from flask.json.tag import JSONTag

class TagOrderedDict(JSONTag):
    __slots__ = ('serializer',)
    key = ' od'

    def check(self, value):
        return isinstance(value, OrderedDict)

    def to_json(self, value):
        return [[k, self.serializer.tag(v)] for k, v in iteritems(value)]

    def to_python(self, value):
        return OrderedDict(value)

app.session_interface.serializer.register(TagOrderedDict, index=0)

{% macro hello(name) %}Hello {{ name }}!{% endmacro %}

hello = get_template_attribute('_cider.html', 'hello')
return hello('World')

app.config.from_pyfile('yourconfig.cfg')

DEBUG = True
SECRET_KEY = 'development key'
app.config.from_object(__name__)

app.config.from_envvar('YOURAPPLICATION_SETTINGS')

export YOURAPPLICATION_SETTINGS='/path/to/config/file'

app.config.from_pyfile(os.environ['YOURAPPLICATION_SETTINGS'])

app.config.from_object('yourapplication.default_config')
from yourapplication import default_config
app.config.from_object(default_config)

app.config['IMAGE_STORE_TYPE'] = 'fs'
app.config['IMAGE_STORE_PATH'] = '/var/app/images'
app.config['IMAGE_STORE_BASE_URL'] = 'http://img.website.com'
image_store_config = app.config.get_namespace('IMAGE_STORE_')

{
    'type': 'fs',
    'path': '/var/app/images',
    'base_url': 'http://img.website.com'
}

from flask import stream_with_context, request, Response

@app.route('/stream')
def streamed_response():
    @stream_with_context
    def generate():
        yield 'Hello '
        yield request.args['name']
        yield '!'
    return Response(generate())

from flask import stream_with_context, request, Response

@app.route('/stream')
def streamed_response():
    def generate():
        yield 'Hello '
        yield request.args['name']
        yield '!'
    return Response(stream_with_context(generate()))

from flask import _request_ctx_stack

def get_session():
    ctx = _request_ctx_stack.top
    if ctx is not None:
        return ctx.session

def log_template_renders(sender, template, context, **extra):
    sender.logger.debug('Rendering template "%s" with context %s',
                        template.name or 'string template',
                        context)

from flask import template_rendered
template_rendered.connect(log_template_renders, app)

def log_template_renders(sender, template, context, **extra):
    sender.logger.debug('Rendering template "%s" with context %s',
                        template.name or 'string template',
                        context)

from flask import before_render_template
before_render_template.connect(log_template_renders, app)

def log_request(sender, **extra):
    sender.logger.debug('Request context is set up')

from flask import request_started
request_started.connect(log_request, app)

def log_response(sender, response, **extra):
    sender.logger.debug('Request context is about to close down.  '
                        'Response: %s', response)

from flask import request_finished
request_finished.connect(log_response, app)

def log_exception(sender, exception, **extra):
    sender.logger.debug('Got exception during processing: %s', exception)

from flask import got_request_exception
got_request_exception.connect(log_exception, app)

def close_db_connection(sender, **extra):
    session.close()

from flask import request_tearing_down
request_tearing_down.connect(close_db_connection, app)

def close_db_connection(sender, **extra):
    session.close()

from flask import appcontext_tearing_down
appcontext_tearing_down.connect(close_db_connection, app)

from contextlib import contextmanager
from flask import appcontext_pushed

@contextmanager
def user_set(app, user):
    def handler(sender, **kwargs):
        g.user = user
    with appcontext_pushed.connected_to(handler, app):
        yield

def test_user_me(self):
    with user_set(app, 'john'):
        c = app.test_client()
        resp = c.get('/users/me')
        assert resp.data == 'username=john'

recorded = []
def record(sender, message, category, **extra):
    recorded.append((message, category))

from flask import message_flashed
message_flashed.connect(record, app)

class MyView(View):
    methods = ['GET']

    def dispatch_request(self, name):
        return 'Hello %s!' % name

app.add_url_rule('/hello/<name>', view_func=MyView.as_view('myview'))

class SecretView(View):
    methods = ['GET']
    decorators = [superuser_required]

    def dispatch_request(self):
        ...

class CounterAPI(MethodView):
    def get(self):
        return session.get('counter', 0)

    def post(self):
        session['counter'] = session.get('counter', 0) + 1
        return 'OK'

app.add_url_rule('/counter', view_func=CounterAPI.as_view('counter'))

@app.route('/')
def index():
    pass

@app.route('/<username>')
def show_user(username):
    pass

@app.route('/post/<int:post_id>')
def show_post(post_id):
    pass

@app.route('/users/', defaults={'page': 1})
@app.route('/users/page/<int:page>')
def show_users(page):
    pass

@app.route('/region/', defaults={'id': 1})
@app.route('/region/<int:id>', methods=['GET', 'POST'])
def region(id):
   pass

def index():
    if request.method == 'OPTIONS':
        # custom options handling here
        ...
    return 'Hello World!'
index.provide_automatic_options = False
index.methods = ['GET', 'OPTIONS']

app.add_url_rule('/', index)

from flask import Flask
app = Flask(__name__)

@app.route('/')
def index():
    return 'Hello World!'

from hypothetical_flask import route

@route('/')
def index():
    return 'Hello World!'

<!doctype html>
<title>Hello HTML5</title>
<div class=header>
  <h1>Hello HTML5</h1>
  <p class=tagline>HTML5 is awesome
</div>
<ul class=nav>
  <li><a href=/index>Index</a>
  <li><a href=/downloads>Downloads</a>
  <li><a href=/about>About</a>
</ul>
<div class=body>
  <h2>HTML5 is probably the future</h2>
  <p>
    There might be some other things around but in terms of
    browser vendor support, HTML5 is hard to beat.
  <dl>
    <dt>Key 1
    <dd>Value 1
    <dt>Key 2
    <dd>Value 2
  </dl>
</div>

<input value="{{ value }}">

onmouseover=alert(document.cookie)

<a href="{{ value }}">click here</a>
<a href="javascript:alert('unsafe');">click here</a>

response.headers['Strict-Transport-Security'] = 'max-age=31536000; includeSubDomains'

response.headers['Content-Security-Policy'] = "default-src 'self'"

response.headers['X-Content-Type-Options'] = 'nosniff'

response.headers['X-Frame-Options'] = 'SAMEORIGIN'

response.headers['X-XSS-Protection'] = '1; mode=block'

app.config.update(
    SESSION_COOKIE_SECURE=True,
    SESSION_COOKIE_HTTPONLY=True,
    SESSION_COOKIE_SAMESITE='Lax',
)

response.set_cookie('username', 'flask', secure=True, httponly=True, samesite='Lax')

# cookie expires after 10 minutes
response.set_cookie('snakes', '3', max_age=600)

app.config.update(
    PERMANENT_SESSION_LIFETIME=600
)

@app.route('/login', methods=['POST'])
def login():
    ...
    session.clear()
    session['user_id'] = user.id
    session.permanent = True
    ...

body = body.replace("\b", "")

def read_file(filename, charset='utf-8'):
    with open(filename, 'r') as f:
        return f.read().decode(charset)

def write_file(filename, contents, charset='utf-8'):
    with open(filename, 'w') as f:
        f.write(contents.encode(charset))

(prefer-coding-system 'utf-8)
(setq default-buffer-file-coding-system 'utf-8)

flask-sqlite3/
    flask_sqlite3.py
    LICENSE
    README

"""
Flask-SQLite3
-------------

This is the description for that library
"""
from setuptools import setup

setup(
    name='Flask-SQLite3',
    version='1.0',
    url='http://example.com/flask-sqlite3/',
    license='BSD',
    author='Your Name',
    author_email='your-email@example.com',
    description='Very short description',
    long_description=__doc__,
    py_modules=['flask_sqlite3'],
    # if you would be using a package instead use packages instead
    # of py_modules:
    # packages=['flask_sqlite3'],
    zip_safe=False,
    include_package_data=True,
    platforms='any',
    install_requires=[
        'Flask'
    ],
    classifiers=[
        'Environment :: Web Environment',
        'Intended Audience :: Developers',
        'License :: OSI Approved :: BSD License',
        'Operating System :: OS Independent',
        'Programming Language :: Python',
        'Topic :: Internet :: WWW/HTTP :: Dynamic Content',
        'Topic :: Software Development :: Libraries :: Python Modules'
    ]
)

import sqlite3
from flask import current_app, _app_ctx_stack

class SQLite3(object):
    def __init__(self, app=None):
        self.app = app
        if app is not None:
            self.init_app(app)

    def init_app(self, app):
        app.config.setdefault('SQLITE3_DATABASE', ':memory:')
        app.teardown_appcontext(self.teardown)

    def connect(self):
        return sqlite3.connect(current_app.config['SQLITE3_DATABASE'])

    def teardown(self, exception):
        ctx = _app_ctx_stack.top
        if hasattr(ctx, 'sqlite3_db'):
            ctx.sqlite3_db.close()

    @property
    def connection(self):
        ctx = _app_ctx_stack.top
        if ctx is not None:
            if not hasattr(ctx, 'sqlite3_db'):
                ctx.sqlite3_db = self.connect()
            return ctx.sqlite3_db

from flask import Flask
from flask_sqlite3 import SQLite3

app = Flask(__name__)
app.config.from_pyfile('the-config.cfg')
db = SQLite3(app)

@app.route('/')
def show_all():
    cur = db.connection.cursor()
    cur.execute(...)

with app.app_context():
    cur = db.connection.cursor()
    cur.execute(...)

db = SQLite3()
# Then later on.
app = create_app('the-config.cfg')
db.init_app(app)

this_is_a_very_long(function_call, 'with many parameters') \
    .that_returns_an_object_with_an_attribute

MyModel.query.filter(MyModel.scalar > 120) \
             .order_by(MyModel.name.desc()) \
             .limit(10)

this_is_a_very_long(function_call, 'with many parameters',
                    23, 42, 'and even more')

items = [
    'this is the first', 'set of items', 'with more items',
    'to come in this line', 'like this'
]

def hello(name):
    print 'Hello %s!' % name

def goodbye(name):
    print 'See you %s.' % name

class MyClass(object):
    """This is a simple docstring"""

    def __init__(self, name):
        self.name = name

    def get_annoying_name(self):
        return self.name.upper() + '!!!!111'

exp = -1.05
value = (item_value / item_count) * offset / exp
value = my_list[index]
value = my_dict['key']

exp = - 1.05
value = ( item_value / item_count ) * offset / exp
value = (item_value/item_count)*offset/exp
value=( item_value/item_count ) * offset/exp
value = my_list[ index ]
value = my_dict ['key']

if method == 'md5':
    pass

if 'md5' == method:
    pass

def foo():
    """This is a simple docstring"""

def bar():
    """This is a longer docstring with so much information in there
    that it spans three lines.  In this case the closing triple quote
    is on its own line.
    """

# -*- coding: utf-8 -*-
"""
    package.module
    ~~~~~~~~~~~~~~

    A brief description goes here.

    :copyright: (c) YEAR by AUTHOR.
    :license: LICENSE_NAME, see LICENSE_FILE for more details.
"""

class User(object):
    #: the name of the user as unicode string
    name = Column(String)
    #: the sha1 hash of the password + inline salt
    pw_hash = Column(String)

$ pip install --upgrade Flask

response = send_file(open('/path/to/file.txt'))

fname = '/path/to/file.txt'

# Just pass the filepath directly
response = send_file(fname)

# Set the MIME-type and ETag explicitly
response = send_file(open(fname), mimetype='text/plain')
response.set_etag(...)

# Set `attachment_filename` for MIME-type guessing
# ETag still needs to be manually set
response = send_file(open(fname), attachment_filename=fname)
response.set_etag(...)

class TraditionalFlask(Flask):
    def make_response(self, rv):
        if isinstance(rv, tuple):
            return self.response_class(*rv)
        return Flask.make_response(self, rv)

$ python flask-07-upgrade.py > patchfile.diff

$ patch -p1 < patchfile.diff

return send_file(my_file_object)
return send_file(my_file_object)

return send_file(my_file_object, add_etags=False)

@app.after_request
def after_request(response):
    g.db.close()
    return response

@app.teardown_request
def after_request(exception):
    if hasattr(g, 'db'):
        g.db.close()

with app.test_client() as client:
    resp = client.get('/')
    # g.db is still bound if there is such a thing

# and here it's gone

app.error_handlers[403] = handle_error

app.register_error_handler(403, handle_error)

@app.errorhandler(403)
def handle_error(e):
    ...

app.debug = DEBUG
app.secret_key = SECRET_KEY

git config --global user.name 'your name'
git config --global user.email 'your email'

git clone https://github.com/{username}/flask
cd flask

git remote add pallets https://github.com/pallets/flask
git fetch pallets

python3 -m venv env
. env/bin/activate
# or "env\Scripts\activate" on Windows

pip install -e ".[dev]"

pre-commit install --install-hooks

git checkout -b your-branch-name origin/1.0.x

git checkout -b your-branch-name origin/master

git push --set-upstream origin your-branch-name

pytest

tox

coverage run -m pytest
coverage report
coverage html
# then open htmlcov/index.html

cd docs
pip install -r requirements.txt
make html

[fetch]
fsckobjects = true

[receive]
fsckObjects = true

`string`	(default) accepts any text without a slash
`int`	accepts positive integers
`float`	accepts positive floating point values
`path`	like `string` but also accepts slashes
`uuid`	accepts UUID strings

URL	Method	Description
`/users/`	`GET`	Gives a list of all users
`/users/`	`POST`	Creates a new user
`/users/<id>`	`GET`	Shows a single user
`/users/<id>`	`PUT`	Updates a single user
`/users/<id>`	`DELETE`	Deletes a single user

path	`u'/π/page.html'`
full_path	`u'/π/page.html?x=y'`
script_root	`u'/myapplication'`
base_url	`u'http://www.example.com/myapplication/π/page.html'`
url	`u'http://www.example.com/myapplication/π/page.html?x=y'`
url_root	`u'http://www.example.com/myapplication/'`

string	accepts any text without a slash (the default)
int	accepts integers
float	like int but for floating point values
path	like the default but also accepts slashes
any	matches one of the items provided
uuid	accepts UUID strings

	HTML4.01	XHTML1.1	HTML5
`<tag/value/` == `<tag>value</tag>`	1
`<br/>` supported			2
`<script/>` supported
should be served as text/html		3
should be served as application/xhtml+xml
strict error handling
inline SVG
inline MathML
`<video>` tag
`<audio>` tag
New semantic tags like `<article>`

Welcome to Flask¶

User’s Guide¶

Foreword¶

What does “micro” mean?¶

Configuration and Conventions¶

Growing with Flask¶

Foreword for Experienced Programmers¶

Thread-Locals in Flask¶

Develop for the Web with Caution¶

Installation¶

Python Version¶

Dependencies¶

Optional dependencies¶

Virtual environments¶

Create an environment¶

Activate the environment¶

Install Flask¶

Living on the edge¶

Install virtualenv¶

Quickstart¶

A Minimal Application¶

What to do if the Server does not Start¶

Old Version of Flask¶

Invalid Import Name¶

Debug Mode¶

Routing¶

Variable Rules¶

Unique URLs / Redirection Behavior¶

URL Building¶

HTTP Methods¶

Static Files¶

Rendering Templates¶

Accessing Request Data¶

Context Locals¶

The Request Object¶

File Uploads¶

Cookies¶

Redirects and Errors¶

About Responses¶

APIs with JSON¶

Sessions¶

Message Flashing¶

Logging¶

Hooking in WSGI Middleware¶

Using Flask Extensions¶

Deploying to a Web Server¶

Tutorial¶

Project Layout¶

Application Setup¶

The Application Factory¶

Run The Application¶

Define and Access the Database¶

Connect to the Database¶

Create the Tables¶

Register with the Application¶

Initialize the Database File¶

Blueprints and Views¶

Create a Blueprint¶

The First View: Register¶

Login¶

Logout¶

Require Authentication in Other Views¶

Endpoints and URLs¶

Templates¶

The Base Layout¶

Register¶

Log In¶

Register A User¶

Static Files¶

Blog Blueprint¶

The Blueprint¶

Index¶

Create¶

Update¶

Delete¶

Make the Project Installable¶

Describe the Project¶

Install the Project¶

Test Coverage¶

Setup and Fixtures¶