On: Problems with Python dependency management

[stavros]

These days, I am extremely happy to be using uv with single scripts. Put this at the start of your script (which has to end in .py):

(EDIT: Sorry, HN doesn't like code, see the start of https://github.com/skorokithakis/calumny/blob/master/calumny... for an example)

The script will run with uv and automatically create a venv and install all dependencies in it. It's fantastic.

The other alternative, if you want to be extra sure, is to create a pex. It'll even bundle the Python interpreter in the executable (or download it if it's not available on the target machine), and will run anywhere with no other dependency (maybe libc? I forget).

[simonw → stavros]

HN displays code just fine if you put four spaces in front of each line, like this:

    #!/usr/bin/env -S uv run
    # /// script
    # requires-python = ">=3.12"
    # dependencies = [
    #     "google-api-python-client",
    #     "google-auth-httplib2",
    #     "google-auth-oauthlib",
    #     "selenium",
    #     "webdriver_manager",
    #     "pydantic",
    # ]
    # ///
    import argparse
    import datetime

I built a tool to help me do that: https://observablehq.com/@simonw/wrap-text-at-specified-widt...

Edit: Huh, two spaces works too:

  #!/usr/bin/env -S uv run
  # /// script
  # requires-python = ">=3.12"

[Jtsummers → simonw]

Two spaces, Reddit is the four spaces one.

  Two spaces
    Four spaces

[cozzyd → Jtsummers]

which is the right choice as :set ts=2 is obviously correct

[Flimm → simonw]

Here are the official formatting guidelines: https://news.ycombinator.com/formatdoc

[stavros → simonw]

Thanks Simon, I guess it was a brain fart, because I'm sure I've used this formatting a lot in the past.

[d4rkp4ttern → stavros]

You can go a step further and have scripts runnable from anywhere without cloning any repo or setting up any venv, directly from PyPi: when you package your lib called `mylib`, define cli scripts under [project.scripts] in your pyproject.toml,

  [project.scripts]
  mytool = "path.to.script:main"

and publish to PyPi. Then anyone can directly run your script via

  uvx --from mylib mytool

As an example, for Langroid (an open-source agent-oriented LLM lib), I have a separate repo of example scripts `langroid-examples` where I've set up some specific scripts to be runnable this way:

https://github.com/langroid/langroid-examples?tab=readme-ov-...

E.g. to chat with an LLM

  uvx --from langroid-examples chat --model ollama/qwen2.5-coder:32b

or chat with LLM + web-search + RAG

  uvx --from langroid-examples chatsearch --model groq/llama-3.3-70b-versatile

[stavros → d4rkp4ttern]

Hm, I think you can just run something with 'uvx <name>' and it'll download and run it, am I misremembering? Maybe it's only when the tool and the lib have the same name, but I think I remember being able to just run 'uvx parachute'.

[d4rkp4ttern → stavros]

You're right, that's only when the tool and lib have the same name. In my case, I have several example scripts that I wanted to make runnable via a single examples lib

[stavros → d4rkp4ttern]

That's a really useful tip, thank you!

[zahlman → stavros]

>Put this at the start of your script (which has to end in .py):

Yes, that format is specified by PEP 723 "Inline script metadata" (https://peps.python.org/pep-0723/). The cause was originally championed by Paul Moore, one of the core developers of Pip, who authored the competing PEP 722 (see also https://discuss.python.org/t/_/29905) and was advocating for the general idea for long before that.

It's also supported by Pipx, via the `run` subcommand. There's at least one pull request to put it directly into Pip, but Moore doesn't seem to think it belongs there.

[stavros → zahlman]

Yep! It's just that uv installs everything fast enough to run scripts comfortably.

[ethbr1 → stavros]

Fwiw, at the bottom the author recommends uv in almost all situations. (Except for non-Python dependencies, in which case Pixi)

[CamperBob2 → stavros]

That looks pretty awesome. What are the drawbacks to using uv? Does it get along with existing pip and conda installations?

[stavros → CamperBob2]

I don't use conda, so I don't know, but it works fine with pip, it just makes its own virtualenv somewhere. It doesn't touch anything else.

[sunshowers → CamperBob2]

One minor drawback I've noticed is that direnv doesn't come with uv support out of the box: https://github.com/direnv/direnv/issues/1250

[infamia → sunshowers]

I'm in the middle of replacing all of my usage of direnv with mise [1]. It does everything direnv/asdf can (for my use cases) plus a lot more. Mise can install a lot of dev software/frameworks [2], run tasks, file watcher all in a compatible manner for *nix OSes. mise is ridiculously good and even minimizes my need for docker locally.

[1] https://mise.jdx.dev/

[2] https://mise.jdx.dev/registry.html

[d4rkp4ttern → CamperBob2]

Poetry -> UV migration is missing: If you already have a project using Poetry, with a large pyproject.toml with many extras and other settings, there currently isn’t a smooth way to port this to UV. Someone can enlighten me if I missed that.

[shlomo_z → CamperBob2]

It is too fast and doesn't give you time to think. :)

Just Kidding! It's amazing. It gets along with existing installations very well.

[nextaccountic → stavros]

Why does it has to end with .py?

[karl42 → nextaccountic]

It doesn't have to. But if it does not end in .py, you have to add the --script (or -s for short) flag to tell it to interpret the file as a python script.

[stavros → karl42]

Oh, they added that? Very nice, I'll update my instructions and scripts, thanks!

[stavros → nextaccountic]

Otherwise uv doesn't recognize it and goes into an infinite loop.