![Basic FLASK Application
from flask import Flask
app = Flask(__name__)
@app.route("/")
def hello_world():
return "<p>Hello, World!</p>"
@app.route('/user/<username>')
def profile(username):
return f"{username}'s profile"
@app.route('/login', methods=['GET', 'POST'])
def login():
if request.method == 'POST':
return do_the_login()
else:
return show_the_login_form()
To run the application: flask run
The URL / will run
this function
The URL
/username/test will
run this function
The URL /login will
run this function](https://image.slidesharecdn.com/flaskflaskrestx-211222083442/85/Flask-Flask-restx-2-320.jpg)
![Useful Functions
Get url of a static file:
url_for('static', filename='style.css')
Render html page:
return render_template('hello.html', variable="value")
Redirect:
redirect(url_for('login'))
Abort:
abort(401)
The request object allows you to access useful properties, such as request.args
(URL args), request.form, request.files and request.method. You can also get
cookies through the request object i.e.
request.cookies.get('username')
from flask import session
session['username'] = "hello"
print(session['username'])](https://image.slidesharecdn.com/flaskflaskrestx-211222083442/85/Flask-Flask-restx-3-320.jpg)
![Global error handlers
You can add global error handlers for specific exceptions or errors
@app.errorhandler(404)
def page_not_found(error):
return render_template('page_not_found.html'), 404
from flask import jsonify
@app.route("/users")def users_api():
users = get_all_users()
return jsonify([user.to_json() for user in users])
Apis – Support for JSON](https://image.slidesharecdn.com/flaskflaskrestx-211222083442/85/Flask-Flask-restx-4-320.jpg)
![Flask-Sqlalchemy (Database)
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI’] = 'sqlite:////tmp/db.db'
db = SQLAlchemy(app)
class User(db.Model):
id = db.Column(db.Integer, primary_key=True)
username = db.Column(db.String(80), unique=True)
email = db.Column(db.String(120), unique=True)
class Post(db.Model):
id = db.Column(db.Integer, primary_key=True)
title = db.Column(db.String(80), nullable=False)
user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
user = db.relationship('User', backref=db.backref('posts',
lazy=True))
The advantage of making relationships is the ability to directly get rows of related table
effortlessly i.e. print(post.user.username)](https://image.slidesharecdn.com/flaskflaskrestx-211222083442/85/Flask-Flask-restx-5-320.jpg)
Flask & Flask-restx
- 1. FLASK & FLASK RESTX An Introduction
- 2. Basic FLASK Application from flask import Flask app = Flask(__name__) @app.route("/") def hello_world(): return "<p>Hello, World!</p>" @app.route('/user/<username>') def profile(username): return f"{username}'s profile" @app.route('/login', methods=['GET', 'POST']) def login(): if request.method == 'POST': return do_the_login() else: return show_the_login_form() To run the application: flask run The URL / will run this function The URL /username/test will run this function The URL /login will run this function
- 3. Useful Functions Get url of a static file: url_for('static', filename='style.css') Render html page: return render_template('hello.html', variable="value") Redirect: redirect(url_for('login')) Abort: abort(401) The request object allows you to access useful properties, such as request.args (URL args), request.form, request.files and request.method. You can also get cookies through the request object i.e. request.cookies.get('username') from flask import session session['username'] = "hello" print(session['username'])
- 4. Global error handlers You can add global error handlers for specific exceptions or errors @app.errorhandler(404) def page_not_found(error): return render_template('page_not_found.html'), 404 from flask import jsonify @app.route("/users")def users_api(): users = get_all_users() return jsonify([user.to_json() for user in users]) Apis – Support for JSON
- 5. Flask-Sqlalchemy (Database) app = Flask(__name__) app.config['SQLALCHEMY_DATABASE_URI’] = 'sqlite:////tmp/db.db' db = SQLAlchemy(app) class User(db.Model): id = db.Column(db.Integer, primary_key=True) username = db.Column(db.String(80), unique=True) email = db.Column(db.String(120), unique=True) class Post(db.Model): id = db.Column(db.Integer, primary_key=True) title = db.Column(db.String(80), nullable=False) user_id = db.Column(db.Integer, db.ForeignKey('user.id')) user = db.relationship('User', backref=db.backref('posts', lazy=True)) The advantage of making relationships is the ability to directly get rows of related table effortlessly i.e. print(post.user.username)
- 6. Flask-restx Flask restx is a fork of flask-restplus, it was made because the original library isn’t actively maintained. Flask-restx provides built-in support for Swagger 2.0, which will automatically provide documentation for endpoints and models. You can also test the api’s using a doc URL, without the need for Postman. Flask-restx comes with decorators that allow programmers to handle what input’s will be allowed of what types, without writing any logic. The responses are also controlled, extra fields can be automatically removed. Moreover, if you return objects, they’re automatically jsonified.
- 7. Example setup from flask import Flask from flask_restx import Api app = Flask(__name__) api = Api(app) @api.route('/hello') class HelloWorld(Resource): def get(self): return {'hello': 'world'} Notice that the function is named “get” which corresponds to the request type.
- 8. Expect & Marshal With model = api.model('Model’, { 'task': fields.String, 'uri': fields.Url('todo_ep’) }) model2 = api.model('Model’, { 'name': fields.String(required=True), }, strict=True) class Todo(Resource): @api.expect(model2) @api.marshal_with(model, skip_none=True) def post(self, **kwargs): return TodoDao(todo_id='my_todo', task='Remember’) @api.expect controls the input, strict means no extra fields are allowed, and required means that the api will fail without the input. You can also do regex pattern matching in the model @api.marshal_with controls the output, Notice that the an object is being returned
- 9. Sample Project Structure - api - user - __init__.py - schema.py - endpoint.py - model - user.py