{"slug": "fastcore-v2", "title": "fastcore v2", "summary": "Fastcore v2 was released in July 2026, removing or relocating several APIs and requiring Python 3.11 or later. The update replaces Param with type annotations, moves async helpers to a new fastcore.aio module, and removes parallel_gen in favor of stdlib patterns. Users needing old APIs can pin fastcore<2.", "body_md": "Note\n\nIn July 2026 we released fastcore v2, which removes or relocates a number of APIs that had accumulated better alternatives. If you use `from fastcore.utils import *`\n\n(or `fastcore.all`\n\n), most of these changes won’t affect you. The breaking changes: `Param`\n\nis gone from `fastcore.script`\n\n; use plain type annotations with docments, or `typing.Annotated[type, \"help\"]`\n\n, optionally with a `dict`\n\nof argparse arguments for advanced features. [ L](https://fastcore.fast.ai/foundation.html#l)’s\n\n`starmap`\n\n, `starfilter`\n\n, and the other `star*`\n\n/`rstar*`\n\nmethods are replaced by the [and](https://fastcore.fast.ai/foundation.html#star)\n\n`star`\n\n[function adapters, which compose with every](https://fastcore.fast.ai/foundation.html#rstar)\n\n`rstar`\n\n[method (e.g.](https://fastcore.fast.ai/foundation.html#l)\n\n`L`\n\n`t.map(star(f))`\n\n); relatedly, `spread`\n\nis replaced by [, and](https://fastcore.fast.ai/foundation.html#star)\n\n`star`\n\n`dspread`\n\nis renamed to [. Async helpers now live in the new](https://fastcore.fast.ai/basics.html#dstar)\n\n`dstar`\n\n`fastcore.aio`\n\nmodule: [,](https://fastcore.fast.ai/aio.html#run_sync)\n\n`run_sync`\n\n[, and](https://fastcore.fast.ai/aio.html#iter_sync)\n\n`iter_sync`\n\n[moved there from](https://fastcore.fast.ai/aio.html#ctx_sync)\n\n`ctx_sync`\n\n`net`\n\n, and [,](https://fastcore.fast.ai/aio.html#maybe_await)\n\n`maybe_await`\n\n[,](https://fastcore.fast.ai/aio.html#then)\n\n`then`\n\n[,](https://fastcore.fast.ai/aio.html#mapa)\n\n`mapa`\n\n[,](https://fastcore.fast.ai/aio.html#acache)\n\n`acache`\n\n[,](https://fastcore.fast.ai/aio.html#reawaitable)\n\n`reawaitable`\n\n[, and the other async utilities moved there from](https://fastcore.fast.ai/aio.html#is_async_callable)\n\n`is_async_callable`\n\n`xtras`\n\n. [and the config file functions moved from](https://fastcore.fast.ai/xtras.html#config)\n\n`Config`\n\n`foundation`\n\nto `xtras`\n\n. `fastcore.net`\n\nlost its request builders (`urlrequest`\n\n, `urlsend`\n\n, `do_request`\n\n, `urlcheck`\n\n) and `clean_type_str`\n\nis gone. `parallel_gen`\n\nis removed; the stdlib\n\n`ProcessPoolExecutor`\n\n`initializer`\n\npattern replaces it (fastai’s `parallel_tokenize`\n\nshows the recipe). Python 3.11 or later is now required. If you need the old APIs, pin `fastcore<2`\n\n.Python is a powerful, dynamic language. Rather than bake everything into the language, it lets the programmer customize it to make it work for them. `fastcore`\n\nuses this flexibility to add to Python features inspired by other languages we’ve loved, mixins from Ruby, and currying, binding, and more from Haskell. It also adds some “missing features” and clean up some rough edges in the Python standard library, such as simplifying parallel processing, and bringing ideas from NumPy over to Python’s `list`\n\ntype.\n\nTo install fastcore run: `conda install fastcore -c fastai`\n\n(if you use Anaconda, which we recommend) or `pip install fastcore`\n\n. For an [editable install](https://stackoverflow.com/questions/35064426/when-would-the-e-editable-option-be-useful-with-pip-install), clone this repo and run: `pip install -e \".[dev]\"`\n\n. fastcore is tested to work on Ubuntu, macOS and Windows (versions tested are those shown with the `-latest`\n\nsuffix [here](https://docs.github.com/en/actions/reference/specifications-for-github-hosted-runners#supported-runners-and-hardware-resources)).\n\n`fastcore`\n\ncontains many features, including:\n\n`fastcore.test`\n\n: Simple testing functions`fastcore.foundation`\n\n: Mixins, delegation, composition, and more`fastcore.xtras`\n\n: Utility functions to help with functional-style programming, parallel processing, and more\n\nTo get started, we recommend you read through [the fastcore tour](https://fastcore.fast.ai/tour.html).\n\nAfter you clone this repository, please run `nbdev_install_hooks`\n\nin your terminal. This sets up git hooks, which clean up the notebooks to remove the extraneous stuff stored in the notebooks (e.g. which cells you ran) which causes unnecessary merge conflicts.\n\nTo run the tests in parallel, launch `nbdev_test`\n\n.\n\nBefore submitting a PR, check that the local library and notebooks match.\n\n- If you made a change to the notebooks in one of the exported cells, you can export it to the library with\n`nbdev_prepare`\n\n. - If you made a change to the library, you can export it back to the notebooks with\n`nbdev_update`\n\n.", "url": "https://wpnews.pro/news/fastcore-v2", "canonical_source": "https://github.com/AnswerDotAI/fastcore", "published_at": "2026-07-11 11:36:50+00:00", "updated_at": "2026-07-11 12:04:58.261245+00:00", "lang": "en", "topics": ["developer-tools"], "entities": ["fastcore", "Python", "fastai"], "alternates": {"html": "https://wpnews.pro/news/fastcore-v2", "markdown": "https://wpnews.pro/news/fastcore-v2.md", "text": "https://wpnews.pro/news/fastcore-v2.txt", "jsonld": "https://wpnews.pro/news/fastcore-v2.jsonld"}}