Heroku Python Support

Last updated November 08, 2023

Heroku supports all popular web frameworks for Python including Django, Flask, and so on.

For a deployment tutorial that uses a sample Django app, see Getting Started on Heroku with Python.

Recognizing a Python App

Heroku automatically recognizes your app as a Python app if it includes a requirements.txt, setup.py, or Pipfile file in its root directory.

When Heroku recognizes a deployed application as a Python application, you see this build output:

$ git push heroku master
-----> Python app detected

Specifying a Python Version

By default, newly created Python apps use the python-3.11.6 runtime. You can also specify a different supported Python version.

Supported Runtimes

  • python-3.12.0 (available on all stacks)
  • python-3.11.6 (available on all stacks; recommended)
  • python-3.10.13 (available on all stacks)
  • python-3.9.18 (available on all stacks)

Deprecated Runtimes

  • python-3.8.18 (available on the Heroku-20 stack only)

If you see “Requested runtime is not available for this stack” errors using one of the supported versions, check that your app is using the latest version of the Python buildpack.

Build Behavior

If your app includes a requirements.txt file, Heroku runs the following command to resolve dependencies:

$ pip install -r requirements.txt

Database Auto-Provisioning

This section is only applicable to accounts created before May 15, 2023 or if you asked Heroku Support to enable auto-provisioning for your account.

A mini Heroku Postgres database automatically provisions on the first deploy of your app if:

Automatic provisioning of a database also populates your app’s DATABASE_URL config var.

A Heroku Postgres database is not automatically provisioned for other Python apps, but you can easily provision one manually.

Checking the Python Buildpack Version

The Python buildpack is what transforms your Python source code into a slug that can be deployed on Heroku.

For the best results, it’s recommended that you use the latest stable version of the buildpack, rather than pinning to a tag or branch or using a fork. Otherwise, some documented features don’t work, and you don’t benefit from future bug fixes or improvements made to the buildpack.

The stable heroku/python buildpack release is also pre-installed in the build environment, so using it improves build performance compared to GitHub URLs.

For more information see Buildpack References.

To check which buildpacks are configured on your app, use the heroku buildpacks CLI command:

$ heroku buildpacks
=== my-example-app Buildpack URL
https://github.com/heroku/heroku-buildpack-python.git

If you see a GitHub URL like in the example or one that’s pinned to a custom branch or tag, then it’s recommended to switch to the heroku/python buildpack. heroku/python is the curated stable buildpack registry release.

To switch buildpacks, first clear the existing buildpacks set on the app using:

$ heroku buildpacks:clear
Buildpacks cleared.

Then add the Python buildpack:

$ heroku buildpacks:add heroku/python
Buildpack added.

Finally, check that the configured buildpacks are correct:

$ heroku buildpacks
=== my-example-app Buildpack URL
heroku/python

If you originally set multiple buildpacks on your app, you must add them in the same order as they were listed in heroku buildpacks previously. For example:

$ heroku buildpacks
=== my-example-app Buildpack URLs
1. heroku-community/example-buildpack
2. https://github.com/heroku/heroku-buildpack-python.git
$ heroku buildpacks:clear
$ heroku buildpacks:add heroku-community/example-buildpack
$ heroku buildpacks:add heroku/python
$ heroku buildpacks
=== my-example-app Buildpack URLs
1. heroku-community/example-buildpack
2. heroku/python

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