Flask (web framework)

Flask is a micro web framework written in Python. It is classified as a microframework because it does not require particular tools or libraries.[2] It has no database abstraction layer, form validation, or any other components where pre-existing third-party libraries provide common functions. However, Flask supports extensions that can add application features as if they were implemented in Flask itself. Extensions exist for object-relational mappers, form validation, upload handling, various open authentication technologies and several common framework related tools.[3]

Flask
Developer(s)Armin Ronacher
Initial releaseApril 1, 2010 (2010-04-01)
Stable release
1.1.2[1]  / 3 April 2020 (3 April 2020)
Repositorygithub.com/pallets/flask
Written inPython
TypeWeb framework
LicenseBSD
Websitepalletsprojects.com/p/flask/

Applications that use the Flask framework include Pinterest and LinkedIn.[4][5]

History

Flask was created by Armin Ronacher of Pocoo, an international group of Python enthusiasts formed in 2004.[6] According to Ronacher, the idea was originally an April Fool's joke that was popular enough to make into a serious application.[7][8][9]

When Ronacher and Georg Brandl created a bulletin board system written in Python, the Pocoo projects Werkzeug and Jinja were developed.[10]

Flask has become popular among Python enthusiasts. As of October 2020, it has second most stars on GitHub among Python web-development frameworks, only slightly behind Django,[11] and was voted the most popular web framework in the Python Developers Survey 2018.[12]

Components

The microframework Flask is based on the Pocoo projects, Werkzeug and Jinja2.

Werkzeug

Werkzeug is a utility library for the Python programming language, in other words a toolkit for Web Server Gateway Interface (WSGI) applications, and is licensed under a BSD License. Werkzeug can realize software objects for request, response, and utility functions. It can be used to build a custom software framework on top of it and supports Python 2.7 and 3.5 and later.[13][14]

Jinja
Main article: Jinja (template engine)

Jinja, also by Ronacher, is a template engine for the Python programming language and is licensed under a BSD License. Similar to the Django web framework, it handles templates in a sandbox.

Features
  • Development server and debugger
  • Integrated support for unit testing
  • RESTful request dispatching
  • Uses Jinja templating
  • Support for secure cookies (client side sessions)
  • 100% WSGI 1.0 compliant
  • Unicode-based
  • Extensive documentation
  • Google App Engine compatibility
  • Extensions available to enhance features desired

Example

The following code shows a simple web application that displays "Hello World!" when visited:

from flask import Flask
app = Flask(__name__)

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


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

See also

References
  1. "Release 1.1.2". 3 April 2020. Retrieved 4 April 2020.
  2. "Flask Foreword". Archived from the original on 2017-11-17.
  3. "Flask Extensions". Archived from the original on 2018-05-17.
  4. What challenges has Pinterest encountered with Flask?
  5. Rachel Sanders: Developing Flask Extensions - PyCon 2014
  6. "Pocoo Team". Archived from the original on 2018-03-15.
  7. Ronacher, Armin. "Opening the Flask" (PDF). Archived from the original (PDF) on 2016-12-17. Retrieved 2011-09-30.
  8. Ronacher, Armin (3 April 2010). "April 1st Post Mortem". Armin Ronacher's Thoughts and Writings. Archived from the original on 2018-05-14. Retrieved 2015-07-25.
  9. "Denied: the next generation python micro-web-framework (April Fools page)". Archived from the original on 2011-09-04. Retrieved 2011-09-30.
  10. "History". Pocoo Team. Archived from the original on 2017-11-19. Retrieved 2015-03-25.
  11. "Python libraries by GitHub stars". Github. Retrieved 2020-01-27.
  12. "Python Developers Survey 2018". www.jetbrains.com. 2018-11-01.
  13. Ronacher, Armin. "Werkzeug The Python WSGI Utility Library". palletsprojects.com. Retrieved 27 May 2018.
  14. Ronacher, Armin. "Installation, Python Version". palletsprojects.com. Retrieved 20 April 2020.
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