pyzstd and stdlib (PEP 784)

[Rogdham]

Python 3.14 introduces the compression.zstd module, adding Zstandard support to the standard library (PEP 784). The CPython implementation was adapted from the pyzstd codebase. As the maintainer of pyzstd, I was contacted by @emmatyping and contributed to this effort.

I believe the future of Zstandard in Python lies in the stdlib, with additional libraries offering extra functionality in pure Python (without the need for a C module). A shared codebase maintained by CPython core developers will mutualize the work (updates, security, performance, etc.), and benefit the entire community.

As a result, below is my personal plan of action:

• Help with PEP 784 and the integration of pyzstd into stdlib ➡️ was done in the last few months.
• Backport the code from stdlib to support for Python versions before 3.14 ➡️ backports.zstd is available.
• Promote adoption of the stdlib and help with migration.
• Use stdlib in pyzstd.

For pyzstd specifically, I am working on the following points:

• Update the readme and documentation to recommend the standard library for new users and provide a migration guide for existing users.
• Deprecate parts of the pyzstd public API that cannot be reimplemented using the standard library.
• Refactor the pyzstd codebase to use stdlib instead of C/CFFI bindings, making pyzstd a pure Python module.

This ticket will be used to gather feedback and track progress on the above plan.

[Rogdham]

Update the readme and documentation to recommend the standard library for new users and provide a migration guide for existing users.

This is now live on the git master branch and the latest version of the documentation.

It will become automatically promoted to the stable version of the documentation on the next release of pyzstd.

[Rogdham]

Deprecate parts of the pyzstd public API that cannot be reimplemented using the standard library.

This has been done in #47. Very few deprecations!

[Rogdham]

Refactor the pyzstd codebase to use stdlib instead of C/CFFI bindings, making pyzstd a pure Python module.

The refactor is happening in #56! There may still be some rough edges, but it is usable at this point.

This took longer than anticipated, due to the SeekableZstdFile class being intertwine with ZstdFile. I managed to get away with this by… refactoring it out in #55.

[Rogdham]

Version 0.19.0 of pyzstd has been released! 🚀

pyzstd is now a pure-python module, relying on compression.zstd (or backports.zstd for Python before 3.14), without any public API changes.

This completes the plan created last September.