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Klein, a Web Micro-Framework

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Klein is a micro-framework for developing production-ready web services with Python. It is 'micro' in that it has an incredibly small API similar to Bottle and Flask. It is not 'micro' in that it depends on things outside the standard library. This is primarily because it is built on widely used and well tested components like Werkzeug and Twisted.

A Klein bottle is an example of a non-orientable surface, and a glass Klein bottle looks like a twisted bottle or twisted flask. This, of course, made it too good of a pun to pass up.

Klein's documentation can be found at Read The Docs.


This is a sample Klein application that returns 'Hello, world!', running on port 8080.

from klein import run, route

def home(request):
    return 'Hello, world!'

run("localhost", 8080)


klein is hosted on GitHub and is an open source project that welcomes contributions of all kinds from the community, including:

For more information about contributing, see the contributor guidelines.