Python classic buildpack updated to Pipenv 2025.0.4
Change effective on 23 July 2025
We have updated the package managers used during the build of Cedar-generation Python apps as follows:
- Pipenv updated from 2024.0.1 to 2025.0.4 (changelog)
In addition, Pipenv is now installed into its own virtual environment to isolate it and its internal dependencies from the app environment. If your app inadvertently relied upon one of Pipenv’s dependencies rather than explicitly declaring the dependency, you will need to update your Pipfile and Pipfile.lock to add the missing dependency.
In particular, if you see the error ModuleNotFoundError: No module named 'pkg_resources' it means your app (or one of its dependencies) relies upon the setuptools package, but that package is missing from Pipfile / Pipfile.lock and must now be added there.
For more details, see the Python classic buildpack changelog.
We recently added support for uv. If you have not used the package manager uv before, we highly recommend giving it a try - it supports lockfiles, is extremely fast, and is actively maintained by a full-time team! Learn more in our blog post Heroku Adds Support for uv.