Topics covered in this episode: Tachyon: A sampling profiler ships in Python 3.15's stdlib Python Workers are now generally available on Cloudflare Flet 1.0 - build cross-platform apps in Python marimo-book: Build static books from marimo notebooks Extras Joke Watch on YouTube Sponsored by Logfire from Pydantic: pythonbytes.fm/logfire Connect with the hosts Michael: Mastodon / BlueSky / X / LinkedIn Calvin: Mastodon / BlueSky / X / LinkedIn Show: Mastodon / BlueSky / X Join us on YouTube at pythonbytes.fm/live to be part of the audience. Usually Tuesday at 7am PT. Older video versions available there too. Finally, if you want an artisanal, hand-crafted digest of every week of the show notes in email form? Add your name and email to our friends of the show list, we'll never share it. Michael #1: Tachyon: A sampling profiler ships in Python 3.15's stdlib Python 3.15 adds the profiling package per PEP 799: profiling.tracing (where cProfile moved) and profiling.sampling, the new sampler called Tachyon py-spy and Austin exist but copy raw interpreter bytes with no API, so every CPython release risks breaking them; one in the stdlib is a contract to stop breaking profilers Defaults: 1 kHz, main thread, wall clock, and a -live top-like view for poking at a slow server Output is flexible: pstats, -flamegraph, -diff-flamegraph against a baseline, -heatmap on source lines, -opcodes for specialized bytecode, -gecko for Firefox Profiler with GIL and GC markers Profiling modes: wall, cpu, gil (which function is starving my other threads?), and exception, plus -async-aware to see the task graph instead of just select(), -all-threads, and -subprocesses forking a profiler per child Near-zero overhead for production; guidance is 10-30 second windows on representative load, and free-threaded builds divide the rate by thread count Attach to a running PID, same minor version only; ptrace permissions are the main friction. A 3.14 backport already exists on GitHub Caveat: it only sees Python frames, so 90% in calculate() hides NumPy underneath. For native stacks there's Cronon from HRT, 200k samples/sec over DWARF, not yet open source Calvin #2: Python Workers are now generally available on Cloudflare Python Workers are out of beta - now GA, "first-class" language on Cloudflare's Developer Platform No more manual JS interop: bindings (queues, R2, D1, Durable Objects) now work natively in Python, e.g. self.env.QUEUE.send({...}) Runs on Pyodide (WASM-compiled Python), with real TCP socket support for DB connectivity Frameworks supported: FastAPI, Django, Flask; AI libs like OpenAI SDK, LangChain, MCP Underlying platform work formalized as PEP 783 (PyEmscripten), after a year of discussion Bottom line: write real Python on Cloudflare's edge, no JS glue code required Calvin #3: Flet 1.0 - build cross-platform apps in Python Flet hits 1.0 - build Flutter-backed apps from pure Python, no frontend experience needed One codebase targets six platforms: iOS, Android, Windows, macOS, Linux, web 150+ built-in UI controls, plus support for custom controls / wrapping Flutter packages Mobile now supports real Python packages: NumPy, pandas, Pillow, cryptography Comes with pytest-based UI testing and an MCP integration for AI coding assistants Milestone lands 4+ years after its first PyPI release (Sept 2022) - signals "production ready," not experimental Michael #4: marimo-book: Build static books from marimo notebooks marimo-book is a Jupyter-Book-style static site generator built specifically for marimo .py notebooks. It ships polished multi-page sites with Material for MkDocs theming, full-text search, dark mode, and code copy, plus a content-hashed incremental build cache that drops rebuilds from 100+ seconds to roughly 3 seconds on real books. Standout extras include anywidget rendering without a kernel, static reactivity for discrete sliders via pre-rendered lookup tables, an opt-in WASM/Pyodide mode per chapter, and per-chapter launch buttons. If you've wanted to publish a marimo notebook as a real book or course site without hosting a kernel, marimo-book gives you the static, searchable, fast-loading output you'd expect from Jupyter Book. Alpha (0.1.x), but in production: pin marimo-book>=0.1.5,0.2; the book.yml schema is stable for v0.1, and dartbrains.org is a real-world user. Two-stage build by design: a marimo-aware preprocessor emits plain Markdown + inline HTML, then mkdocs (Material today, zensical tomorrow) renders it. Not a mkdocs plugin, so the shell stays swappable. Interactive widgets without a kernel: anywidget Canvas/Three.js/Plotly mounts render statically, and mo.ui.slider with explicit steps gets pre-computed as a static lookup table. WASM escape hatch per chapter: set mode: wasm and the chapter routes through marimo's MarimoIslandGenerator, shipping the marimo runtime + Pyodide bundle for full reactivity where you need it. Per-chapter launch buttons and extras: readers can jump to molab, GitHub, or a downloaded .py; optional [social], [linkcheck], and [pdf] extras cover OG cards, htmlproofer, and WeasyPrint PDF export. Sandboxed notebooks: the sandbox mode reads PEP 723 inline metadata and provisions per-notebook envs via uv for portable builds, at the cost of slower first runs. Extras Calvin: Great overview of a new feature in Python 3.15 - frozendict Michael: Microsoft Plugs Nearly 1,000 Security Holes in Windows I’ll be speaking at PyBay 2026 PyCon NL on October 15 in Utrecht Heading to Europe in October? PyCon NL is October 15th in Utrecht. One day, three tracks, about 350 people. It's an hour by train from Schiphol. There's also a session just for community organizers from groups like PyLadies, PyData, and Django. And the location fits. The Netherlands is where Python itself was born. Joke: You have homework (no really ;) ) Watch Interview with Big Data engineer in 2026 by Kai Lentit
