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Flask (programming)

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Title: Flask (programming)  
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Subject: Comparison of web application frameworks, Web2py, Server-side scripting, AppJet, Knockout (web framework)
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Flask (programming)

Developer(s) Armin Ronacher
Initial release April 1, 2010 (2010-04-01)
Stable release 0.10.1 / June 14, 2013 (2013-06-14)[1]
Written in Python
Operating system Cross-platform
Type Web application framework
License BSD
Website .org.pocooflask

Flask is a lightweight web application framework written in Python and based on the WSGI toolkit and Jinja2 template engine. It is BSD licensed.

Flask takes the flexible Python programming language and provides a simple template for web development. Once imported into Python, Flask can be used to save time building web applications. An example of an application that is powered by the Flask framework is the community web page for Flask.[2]

Flask is called a microframework because it keeps the core simple but extensible. 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 more.


Flask was created by Armin Ronacher. "It came out of an April Fool's joke but proved popular enough to make into a serious application in its own right."[3][4]


  • Contains development server and debugger
  • Integrated support for unit testing
  • RESTful request dispatching
  • Uses Jinja2 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.


The following code shows a simple web application that prints "Hello World!":

from flask import Flask
app = Flask(__name__)

def hello():
    return "Hello World!"

if __name__ == "__main__":

See also


  1. ^
  2. ^ Community web page for Flask
  3. ^ Ronacher, Armin. "Opening the Flask". Retrieved September 30, 2011. 
  4. ^ "Denied: the next generation python micro-web-framework (April Fools page)". Retrieved September 30, 2011. 

External links

  • Flask website
  • Flask documentation
  • Project source code on Github
  • Flask on PyPI
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