Flask quick start

quickstart.py

from flask import Flask, escape, url_for, request, redirect, session
from werkzeug.utils import secure_filename

#Instancier une application Flask
app = Flask(__name__)

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

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


@app.route('/hello')
def hello():
    return 'Hello, world 2'

#route with string param
@app.route('/user/<username>')
def show_user_profile(username):
    return 'User {}'.format(username)

#route with integer param
@app.route('/post/<int:post_id>')
def show_post(post_id):
    return 'Post %d' % post_id

#route with path param
@app.route('/path/<path:subpath>')
def show_subpath(subpath):
    return 'Subpath {}'.format(subpath)


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

#get the url of a fuction or a static file
with app.test_request_context():
    print(url_for('profile', username="John"))
    print(url_for('show_post', post_id=1))
    print(url_for('show_subpath', subpath="home"))
    print(url_for('static', filename='style.css'))

#Can be usefull for unit testing
with app.test_request_context('/hello', method='POST'):
    assert request.path == '/hello'
    assert request.method == 'POST'

#Other way to make a test
with app.request_context(environ):
    assert request.method == 'POST'

#Handle multiple request type with a function
@app.route('/login', methods=['GET', 'POST'])
def login():
    if request.method == 'POST':
        return do_the_login()
    else:
        return show_the_login_form()

#Randering template with flask, jinja2 work like django template
@app.route('/home/<string:name>')
def home(name):
    return render_template('home.html', name=name)

#Request object in details
@app.route('/login_2', 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'

    return render_template('login.html', error=error)

#get params of a request
@app.route('/params', methods=['GET'])
def params():
    try:
        searchword = request.args.get('key', '')
    except KeyError:
        return 'Bad key provided'

    return searchword

#handle File Upload with flask
@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))


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

#raise http errors
def login():
    abort(401)
    this_is_never_executed()

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

#Returning JSON With dict object
@app.route("/me")
def me_api():
    user = get_current_user()
    return {
        "username": user.name,
        "theme": user.theme,
        "image": url_for("user_image", filename=user.image)
    }

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

#Manage sessions 
@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'))

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