Python: Performance Fixes and Security Updates

Transcript

Good morning, this is your Python development briefing for May 30th, 2026.

TomiBelan merged a significant performance fix for tarfile reading with "r|*" mode, resolving issue 121109. The change eliminates orders-of-magnitude slowdowns when using list operations on streaming tar files, bringing performance in line with regular mode operations.

Esadomer delivered performance improvements to logging.config, specifically speeding up fileConfig and dictConfig when handling existing loggers. The optimization replaces inefficient list operations with set-based membership tracking and binary search algorithms.

Several critical bug fixes landed today. Serhiy Storchaka fixed ElementTree HTML serialization, correcting how comments, processing instructions, and specific HTML elements like iframe and plaintext are handled. The same author also resolved a crash in the XML parser when processing invalid XML with multi-byte encodings.

Thomas Kowalski fixed a parameter passing issue in the json module where the array_hook parameter wasn't properly forwarded from json.load to json.loads, and Grant Herman addressed an asyncio sendfile fallback bug that was ignoring non-zero offset values.

Documentation received important updates, including a new security warning for pydoc's HTTP server and proper documentation for the frozendict type in the language reference. Jonathan Dung corrected the inspect.getattr_static documentation signature.

Multiple pull requests were automatically backported to Python versions 3.13, 3.14, and 3.15, ensuring these fixes reach all supported releases.

What's next: Watch for continued performance optimizations in core libraries and additional security documentation improvements.

That's your Python development update. We'll be back tomorrow with the latest from the CPython repository.