Flask (web framework)
|Initial release||April 1, 2010|
1.1.2 / 3 April 2020
Flask is a micro web framework written in Python. It is classified as a microframework because it does not require particular tools or libraries. 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.
Flask was created by Armin Ronacher of Pocoo, an international group of Python enthusiasts formed in 2004. According to Ronacher, the idea was originally an April Fool's joke that was popular enough to make into a serious application.
Flask has become popular among Python enthusiasts. As of October 2020[update], it has second most stars on GitHub among Python web-development frameworks, only slightly behind Django, and was voted the most popular web framework in the Python Developers Survey 2018.
The microframework Flask is based on the Pocoo projects, Werkzeug and Jinja2.
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.
- 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
- Extensive documentation
- Google App Engine compatibility
- Extensions available to enhance features desired
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)
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