Flask Python Library Cheatsheet

Flask, a lightweight and versatile web framework for Python, has gained immense popularity for its simplicity and flexibility. Whether you’re a beginner or an experienced developer, having a Flask cheatsheet handy can save you time and effort in your web development endeavors. In this blog post, we’ll provide a comprehensive Flask cheatsheet to help you navigate through the essential concepts and commands.

Getting Started

Installation

pip install Flask

Basic App Structure

from flask import Flask

app = Flask(__name__)

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

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

Routing

Basic Routes

@app.route('/')
def index():
    return 'Welcome to the homepage!'

@app.route('/about')
def about():
    return 'About Us'

Route with Variable

@app.route('/user/<username>')
def show_user_profile(username):
    return f'User {username}'

Request Handling

Accessing Request Data

from flask import request

@app.route('/login', methods=['POST', 'GET'])
def login():
    if request.method == 'POST':
        return f'Logged in as {request.form["username"]}'
    else:
        return 'Login Page'

Query Parameters

from flask import request

@app.route('/search')
def search():
    query = request.args.get('query')
    return f'Searching for: {query}'

Templates

Rendering HTML Templates

from flask import render_template

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

Static Files

Serving Static Files

# Create a folder named 'static' in your project directory
# Place your static files (CSS, JS, images) inside the 'static' folder

# Access static files in templates
<link rel="stylesheet" href="{{ url_for('static', filename='style.css') }}">

Forms

WTForms Integration

pip install Flask-WTF

from flask_wtf import FlaskForm
from wtforms import StringField, SubmitField

class MyForm(FlaskForm):
    username = StringField('Username')
    submit = SubmitField('Submit')

Flask-RESTful

RESTful APIs with Flask-RESTful

pip install Flask-RESTful

from flask_restful import Resource, Api

app = Flask(__name__)
api = Api(app)

class HelloWorld(Resource):
    def get(self):
        return {'hello': 'world'}

api.add_resource(HelloWorld, '/')

Error Handling

Handling 404 Error

from flask import render_template

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

Deployment

Deployment Options

• Development Server:

  flask run

• Production Server (Gunicorn):

  pip install gunicorn
  gunicorn -w 4 -b 0.0.0.0:8000 myapp:app

• Docker:

  docker build -t myflaskapp .
  docker run -p 4000:80 myflaskapp

This Flask cheatsheet serves as a quick reference guide to help you build web applications with Flask efficiently. As you delve deeper into Flask development, you may explore additional features and extensions to enhance your projects. Keep this cheatsheet handy, and may your Flask journey be smooth and productive!

FAQ