Flask

Flask is a lightweight WSGI_ web application framework. It is designed to make getting started quick and easy, with the ability to scale up to complex applications. It began as a simple wrapper around Werkzeug_ and Jinja_ and has become one of the most popular Python web application frameworks.

Flask offers suggestions, but doesn't enforce any dependencies or project layout. It is up to the developer to choose the tools and libraries they want to use. There are many extensions provided by the community that make adding new functionality easy.

.. _WSGI: https://wsgi.readthedocs.io/ .. _Werkzeug: https://werkzeug.palletsprojects.com/ .. _Jinja: https://jinja.palletsprojects.com/

Installing

Install and update using pip_:

.. code-block:: text

$ pip install -U Flask

.. _pip: https://pip.pypa.io/en/stable/quickstart/

A Simple Example

.. code-block:: python

# save this as app.py
from flask import Flask

app = Flask(__name__)

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

.. code-block:: text

$ flask run
  * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

Contributing

For guidance on setting up a development environment and how to make a contribution to Flask, see the contributing guidelines_.

.. _contributing guidelines: https://github.com/pallets/flask/blob/main/CONTRIBUTING.rst

Donate

The Pallets organization develops and supports Flask and the libraries it uses. In order to grow the community of contributors and users, and allow the maintainers to devote more time to the projects, please donate today_.

.. _please donate today: https://palletsprojects.com/donate

Links

• Documentation: https://flask.palletsprojects.com/
• Changes: https://flask.palletsprojects.com/changes/
• PyPI Releases: https://pypi.org/project/Flask/
• Source Code: https://github.com/pallets/flask/
• Issue Tracker: https://github.com/pallets/flask/issues/
• Website: https://palletsprojects.com/p/flask/
• Twitter: https://twitter.com/PalletsTeam
• Chat: https://discord.gg/pallets