$ ls
Procfile  requirements.txt  web.py

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

$ git push heroku master
...
-----> Fetching custom git buildpack... done
-----> Python app detected
-----> No runtime.txt provided; assuming python-2.7.6.
-----> Preparing Python runtime (python-2.7.6)
-----> Installing Setuptools (2.1)
-----> Installing Pip (1.5.2)
-----> Installing dependencies using Pip (1.5.2)
       Downloading/unpacking Flask==0.7.2 (from -r requirements.txt (line 1))
       Downloading/unpacking Werkzeug>=0.6.1 (from Flask==0.7.2->-r requirements.txt (line 1))
       Downloading/unpacking Jinja2>=2.4 (from Flask==0.7.2->-r requirements.txt (line 1))
       Installing collected packages: Flask, Werkzeug, Jinja2
       Successfully installed Flask Werkzeug Jinja2
       Cleaning up...

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

$ heroku config:add BUILDPACK_URL=git://github.com/heroku/heroku-buildpack-python.git

The buildpack will detect your app as Python if it has the file requirements.txt in the root.

It will use Pip to install your dependencies, vendoring a copy of the Python runtime into your slug.

Specify a Runtime

You can also provide arbitrary releases Python with a runtime.txt file.

$ cat runtime.txt
python-3.3.3

Runtime options include:

python-2.7.6
python-3.3.3
pypy-1.9 (experimental)

Other unsupported runtimes are available as well.