xz Compression in Python: A Comparison with BSD tar

When it comes to compressing large files, the choice of compression method and tool can have a significant impact on the final size of the archive. In this article, we'll explore the differences between using the `xz` compression algorithm with the `tar` command versus Python's built-in `tarfile` library.

To test the efficiency of these methods, I created an archive containing 1440 JSON files, totaling around 1.3 GB in size. Using the `tar` command on my Mac with Homebrew installed GNU tar (`gtar`), I created an archive using the default settings and then repeated the process with the `-sort` option set to `name`. In contrast, Python's `tarfile` library was used to create a compressed archive with the same directory structure.

The results were striking. The archive created by the `tar` command was approximately 1.5 MB in size, while the one generated by the `tarfile` library was only around 100 KB. This 15-fold difference may seem alarming, leading some to wonder if there's an issue with the Python implementation.

Upon closer inspection, it appears that the underlying cause of this discrepancy lies in the way each method handles file ordering within the archive. By default, BSD tar and GNU tar without any sort options store files in an undefined order, which can lead to differences in the final compressed size. In contrast, the `tarfile` library sorts files by modification date.

To verify these findings, I extracted both archives using Quicklook (with the Betterzip plugin) and compared them directly using the `diff` command. The results showed that the files within each archive were indeed ordered differently, with the Python archive following a more predictable ordering scheme.

In conclusion, it's safe to use Python's built-in `tarfile` library for compressing data without worrying about losing any information or compromising data integrity. While there may be some differences in file ordering between the two methods, these differences are not indicative of an issue with the Python implementation.

If you're looking for a reliable and efficient way to compress large files, consider using the `tarfile` library in your Python applications. With its built-in support for `xz` compression, it's well-suited for tasks that require fast and compact storage solutions.

Xz compression python