Recommended web frameworks include Django and Flask. Recommended webserver is Gunicorn. There are no restrictions around what software can be used (as long as it's pip-installable). Web processes must bind to $PORT, and only the HTTP protocol is permitted for incoming connections.

Usage

Example usage:

$ ls
Procfile  requirements.txt  web.py

$ heroku create --buildpack git://github.com/heroku/heroku-buildpack-python.git

$ git push heroku master
...
-----> Python app detected
-----> Installing python-2.7.11
     $ pip install -r requirements.txt
       Collecting requests (from -r requirements.txt (line 1))
         Downloading requests-2.9.1-py2.py3-none-any.whl (501kB)
       Installing collected packages: requests
       Successfully installed requests-2.9.1
       
-----> Discovering process types
       Procfile declares types -> (none)

You can also add it to upcoming builds of an existing application:

$ heroku buildpacks:set heroku/python

A requirements.txt file must be found at the root of your application's repository.

Specify a Runtime

You can also specify specific versions of the Python runtime with a runtime.txt file:

$ cat runtime.txt
python-3.5.1

Runtime options include:

python-2.7.11
python-3.5.1
pypy-4.0.1 (unsupported, experimental)
pypy3-2.4.0 (unsupported, experimental)

Other unsupported runtimes are available as well. Use at your own risk.