A detailed example of the pylock.toml format is available in PEP 751. Each dependency has its own [[packages]] subsection, with details about where and when it was obtained, its hash, version requirements, and so on. The example shows how a package can have multiple platform-specific sources. In the example, numpy lists binary wheels for Microsoft Windows and generic Linux systems.
When will PEP 751 lock files arrive?
As of this writing, there’s no official or third-party tool that supports pylock.toml today. Future revisions of tools, from pip on outwards, are meant to adopt pylock.toml at the pace their providers find suitable, so you can expect the new lock file to be added to workflows and to the makeup of projects over time. You will eventually want to think about whether the set of dependencies of your project is complex enough to demand a pylock.tomlfile. Anyone creating a package hosted on PyPI, for instance, will want to gravitate towards creating a pylock.toml for the project.
The speed of adoption will be dictated by how soon existing tools make it possible to generate pylock.toml files, and whether that file format will immediately replace their own internal formats. Some third-party tools that generate their own lock files remain hesitant to use pylock.toml as a full replacement. uv, for instance, intends to support pylock.toml as an export and import format, but not as the format for its native lock files due to some features not yet supported in pylock.toml. However, it’s entirely possible that support for those features could be added to future revisions of the pylock.toml spec.