Is it? Every time nixpkgs changes the python minor version all of my virtualenvs break, which is a pain. I guess I need to look into dev shell or something.
Yes you need to use a shell to make it reproducible in the nix sense; a regular venv will try to point to the nix store or lose libraries (or try to dynamic-link stuff) when your system env changes which is why you need it to be independent of it.
I don’t bother with venvs in my own projects because nix kind of subsumes its purpose, but it’s possible to work with them still.
Something that might help: devenv. I haven’t used this personally but the UX looks like an upgrade. (I just use flakes with dev shells defined inline long-form)
If you don’t use a venv at all, do you add every new requirement to your main config.nix?
If it matters, I’m not a real developer. I don’t deploy or package anything. I’m just making tools for my own work. I’m not concerned about Nix-like reproducibility for my python scripts because they’re pretty simple and only live on my machine.
In ‘proper’ software development projects, you (ideally) want all information checked into the repo for what is needed to run the software:
which dependencies you need,
what particular versions of the dependencies,
as well as which runtime/compiler version to use.
And then you’d use a package manager which can automatically install all these.
Python projects are currently heavily moving towards uv for this. Traditionally, you’d use pip + virtualenv + sometimes pipx for this.
You can check out a commit from months ago and just run it right away. Well, or just a commit from yesterday, which is on a different Git branch, where you haven’t yet started your big dependency upgrade. As soon as upgrading a dependency requires changes in your code, you want the dependency version change tracked together with the respective code change.
Your different team mates can all work on the repository, even though one of them might be on Debian, the next on Arch and the third is on macOS. By defining all your dependencies in the repo, you can avoid “works on my machine” scenarios, where a bug occurs on one PC, but not on the dev’s PC where you try to reproduce it.
No, not to my nixos configuration. In fact I don’t even have a global / system / user-wide Python interpreter. I rely on nix shells and package closures; no imperative use of python.
I’m not a big python dev; my meaningful experience is with systems languages. But for a release or project i intend to be consumed outside of nix, I’ll use venvs and a requirements file because that’s just the right way to do things.
But what I meant was that I’d use a nix shell or build package that uses py libs that are already packaged for nix, or package the ones that aren’t myself, and just use the nix closure as my venv; no regular venv or pip workflow.
Devenv seems to let you just point at a requirements file and it builds the venv for you. Very clean for portability beyond nix consumers that way. But most of my Python projects are personal utilities and can target nix exclusively.
Which manages uv and pyenv and stuff for python, and package managers for just about every other language I dev in.
It’s version managers all the way down lol, but it’s the only way I’ve found to have proper declarative versions within my nix config that don’t rely on the nixpkgs ecosystem changing, and doesn’t require manually managing a package manager for every single language I use
Is it? Every time nixpkgs changes the python minor version all of my virtualenvs break, which is a pain. I guess I need to look into dev shell or something.
Yes you need to use a shell to make it reproducible in the nix sense; a regular venv will try to point to the nix store or lose libraries (or try to dynamic-link stuff) when your system env changes which is why you need it to be independent of it.
I don’t bother with venvs in my own projects because nix kind of subsumes its purpose, but it’s possible to work with them still.
Something that might help: devenv. I haven’t used this personally but the UX looks like an upgrade. (I just use flakes with dev shells defined inline long-form)
This video came across my feed last night, and might give you a rough idea: https://youtu.be/jldArhyi6jM&t=581
If you don’t use a venv at all, do you add every new requirement to your main config.nix?
If it matters, I’m not a real developer. I don’t deploy or package anything. I’m just making tools for my own work. I’m not concerned about Nix-like reproducibility for my python scripts because they’re pretty simple and only live on my machine.
In ‘proper’ software development projects, you (ideally) want all information checked into the repo for what is needed to run the software:
And then you’d use a package manager which can automatically install all these.
Python projects are currently heavily moving towards
uvfor this. Traditionally, you’d usepip+virtualenv+ sometimespipxfor this.Using
nix developwith flakes is also valid for this, if your team agrees on it: https://nixos.wiki/wiki/Development_environment_with_nix-shell#nix_developWhichever way you solve it, the idea is that:
No, not to my nixos configuration. In fact I don’t even have a global / system / user-wide Python interpreter. I rely on nix shells and package closures; no imperative use of python.
I’m not a big python dev; my meaningful experience is with systems languages. But for a release or project i intend to be consumed outside of nix, I’ll use venvs and a requirements file because that’s just the right way to do things.
But what I meant was that I’d use a nix shell or build package that uses py libs that are already packaged for nix, or package the ones that aren’t myself, and just use the nix closure as my venv; no regular venv or pip workflow.
Devenv seems to let you just point at a requirements file and it builds the venv for you. Very clean for portability beyond nix consumers that way. But most of my Python projects are personal utilities and can target nix exclusively.
For most dev libraries I use
https://github.com/nix-community/home-manager
Which manages
https://github.com/jdx/mise
Which manages uv and pyenv and stuff for python, and package managers for just about every other language I dev in.
It’s version managers all the way down lol, but it’s the only way I’ve found to have proper declarative versions within my nix config that don’t rely on the nixpkgs ecosystem changing, and doesn’t require manually managing a package manager for every single language I use
I use home-manager too, but maybe I’m not leveraging it enough since I’m the only user. I’ll look at Mise, thanks.