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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:

Joke: You have homework (no really ;) )

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