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Fun with uv and PEP 723

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619 points deepakjois | 2 comments | 24 Jun 25 18:41 UTC | HN request time: 0s | source
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jkingsman ◴[24 Jun 25 19:19 UTC] No.44369910[source]▶
uv has been fantastic to use for little side projects. Combining uv run with `uv tool run` AKA `uvx` means one can fetch, install within a VM, and execute Python scripts from Github super easily. No git clone, no venv creation + entry + pip install.

And uv is fast — I mean REALLY fast. Fast to the point of suspecting something went wrong and silently errored, when it fact it did just what I wanted but 10x faster than pip.

It (and especially its docs) are a little rough around the edges, but it's bold enough and good enough I'm willing to use it nonetheless.

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lxgr ◴[24 Jun 25 19:31 UTC] No.44370062[source]▶
Truly. uv somehow resolves and installs dependencies more quickly than pyenv manages to print its own --help output.
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mikepurvis ◴[24 Jun 25 20:03 UTC] No.44370440[source]▶
I know there are real reasons for slow Python startup time, with every new import having to examine swaths of filesystem paths to resolve itself, but it really is a noticeable breath of fresh air working with tools implemented in Go or Rust that have sub-ms startup.
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1. mr_mitm ◴[25 Jun 25 07:24 UTC] No.44374512[source]▶
You don't have to import everything just to print the help. I try to avoid top-level imports until after the CLI arguments have been parsed, so the only import until then is `argparse` or `click`. This way, startup appears to be instant even in Python.

Example:

    if __name__ == "__main__":
        from myapp.cli import parse_args

        args = parse_args()

        # The program will exit here if `-h` is given

        # Now do the heavy imports

        from myapp.lib import run_app

        run_app(args)
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2. mikepurvis ◴[25 Jun 25 19:39 UTC] No.44381127[source]▶
Another pattern, though, is that a top level tool uses pkg_resources and entry_points to move its core functionality out to verb plugins— in that case the help is actually the worst case scenario because not only do we have to scan the filesystem looking for what plugins are available, they all have to be imported in order to ask each for its help strings.

An extreme version of this is the colcon build tool for ROS 2 workspaces:

https://github.com/colcon/colcon-core/blob/master/setup.cfg#...

Unsurprisingly, startup time for this is not great.