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


pip install Flask

Basic App Structure

from flask import Flask

app = Flask(__name__)

def home():
    return 'Hello, World!'

if __name__ == '__main__':


Basic Routes

def index():
    return 'Welcome to the homepage!'

def about():
    return 'About Us'

Route with Variable

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"]}'
        return 'Login Page'

Query Parameters

from flask import request

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


Rendering HTML Templates

from flask import render_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') }}">


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')


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

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


Deployment Options

  • Development Server:
  flask run
  • Production Server (Gunicorn):
  pip install gunicorn
  gunicorn -w 4 -b 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!


1. What is Flask and how does it differ from other web frameworks?

Flask is a lightweight web framework for Python that simplifies web development. It is known for its simplicity and flexibility, allowing developers to choose their components. Unlike heavier frameworks like Django, Flask doesn’t impose a specific project structure, making it ideal for small to medium-sized projects where a minimalistic approach is preferred.

2. How can I handle form submissions in Flask?

Handling form submissions in Flask can be achieved with the help of the Flask-WTF extension. This extension integrates the WTForms library into Flask, providing a convenient way to define, validate, and render forms. By creating a form class using Flask-WTF, you can easily handle form data in your routes.

3. What is the purpose of static files in Flask, and how are they served?

Static files in Flask include CSS, JavaScript, and image files that contribute to the styling and functionality of your web application. These files are stored in a folder named ‘static’ within your project directory. To serve static files in templates, you can use the url_for function to generate the correct URLs.

4. How do I deploy a Flask application for production?

Flask applications can be deployed in various ways. For development purposes, the built-in development server can be used with flask run. However, for production, it is recommended to use production-ready servers such as Gunicorn. Docker is another popular option for containerization, providing a consistent environment for your Flask app.

5. Can Flask be used to create RESTful APIs, and what is Flask-RESTful?

Yes, Flask is well-suited for building RESTful APIs. Flask-RESTful is an extension that simplifies the creation of RESTful APIs in Flask. It provides tools for defining resources, handling request parsing, and managing API routes. With Flask-RESTful, you can structure your API in a clean and organized manner, making it easier to develop and maintain.