this post was submitted on 23 Nov 2024
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Python

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constraint vs requirement. What's the difference? (programming.dev)
submitted 4 days ago* (last edited 4 days ago) by [email protected] to c/[email protected]
24 comments fedilink hide all child comments
 

In a requirements-*.in file, at the top of the file, are lines with -c and -r flags followed by a requirements-*.in file. Uses relative paths (ignoring URLs).

Say have docs/requirements-pip-tools.in

-r ../requirements/requirements-prod.in
-c ../requirements/requirements-pins-base.in
-c ../requirements/requirements-pins-cffi.in

...

The intent is compiling this would produce docs/requirements-pip-tool.txt

But there is confusion as to which flag to use. It's non-obvious.

constraint

Subset of requirements features. Intended to restrict package versions. Does not necessarily (might not) install the package!

Does not support:

  • editable mode (-e)

  • extras (e.g. coverage[toml])

Personal preference

  • always organize requirements files in folder(s)

  • don't prefix requirements files with requirements-, just doing it here

  • DRY principle applies; split out constraints which are shared.

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[–] [email protected] 1 points 3 days ago (1 children)

Was working under the assumption that everyone considered constraints (-c) to be non-negotiable required feature.

If only have requirements (-r), in a centralized pyproject.toml, then how to tackle multiple specific dependency hell issues without causing a huge amount of interconnected clutter?

[–] [email protected] 2 points 3 days ago (1 children)

Why do you need to have a centralized pyproject.toml?

[–] [email protected] 1 points 3 days ago (2 children)

Within the context of resolving dependency conflicts, poetry decided pyproject.toml is a great place to put requirements.

This is what people know.

pyproject.toml or venv management should otherwise never come into the conversation.

My personal opinion is: venv, pip, pyenv, pip-tools, and tox are sufficient to manage venvs.

venvs are not required to manage requirement files. It's a convenience so dev tools are accessible.

Currently the options are: poetry or uv.

With honorable mention to pip-compile-multi, which locks dependencies.

poetry and uv manage venvs... Why?

[–] [email protected] 1 points 3 days ago (1 children)

I was asking why you need to have a centralized pyproject.toml file, which is apparently why you need constraint files? Most people don't have this workflow, so are not even aware of constraint files, much less see them as a must-have.

[–] [email protected] 1 points 1 day ago (1 children)

I totally agree with you. So not the best champion of the poetry approach. Someone else would need to step forward, even as devils advocate, and champion poetry. Even if tongue in cheek. Anyone?

Normally, there is no connection between constraint files and pyproject.toml

Python appears to be forever stuck with plain text requirement|constraint files. So putting them into pyproject.toml is just adding an extra layer of complexity.

[–] [email protected] 1 points 1 day ago (1 children)

If most people prefer pyproject.toml over requirements.txt, even if it does not support everything you need, isn't it more likely that you will have to change workflow rather than python remaining stuck with requirement.txt?

[–] [email protected] 1 points 4 hours ago* (last edited 4 hours ago)

more likely

That almost sounds like you might consider to jump on polymarket, initiate the prediction, put money down on that prediction creating a position, but need a little nudge.

Are you willing to make that bet? The size of the bet reflects how strongly you feel. Are you going to make this interesting?

The other side of that bet would be:

Could become that guy who extends the theory, makes a better way of doing it, and creates and publishes the package and docs.

And the world+dog recognizes the package amongst the other tools in this genre, rather than i conforming to existing tools (uv or poetry or pip-compile-multi).

In your favor, there are three tools. So three people/teams on this planet have presented a solution. Can count that on one hand with fingers to spare!

On the other hand, lets keep in mind, this is a Python specific forum and everyone here are skilled super talented coders and probably full on freak'n geniuses (lifts hand, pinky to closest edge of mouth, everyone looks around at one another and copies, then looks back at you with an errie almost coordinated synchronized eye brow raise). And i oddly posted about this exact topic. Literally anyone and everyone who has commented could be that guy.

scratches head

looks up with one eye to check star positions

rubs chin

occasional alternating strong eye brow movements ...

(with hand on chin) who is this guy, should i call his bluff by taking a position? Whats the likelihood he's secretly a closet poetry user and just some poser?

If you won, could you be sad?

If you lost, not get upset or ego hurt instead be much happier with the published tool over the money?

What are the odds looking like on this particular prediction?

Looking forward to you posting the URL to the prediction on polymarket then promoting the market to maximize your returns. First in and clean house. Rinse wash and repeat with this blowhard wannabe (referring to myself).

[–] [email protected] 1 points 3 days ago (1 children)

are you really asking why use 1 tool instead of 5?

venvs and dependency management are such interconnected concepts, I don't even know how you could sustainably handle them separately.

[–] [email protected] 1 points 3 days ago* (last edited 3 days ago) (1 children)

UNIX philosophy. One tool that does one thing well

Best to have a damn good reason when breaking this principle (e.g. vendoring) or be funded by Money McBags

requirements files are requirements files, not venvs. They may install into venv, but they are not venvs themselves. The only thing a venv provides that is of interest to ur requirements files are: the relative folder path (e.g. '.venv') and python interpreter path. Nothing more. When using tox, the py version is hardcoded, so only need to provide the relative folder path.

The venv management tools we have are sufficient. the problem is not the venv, it's managing the requirements files.

Your 1 tool suacks just as much as my 5 tools when it comes to managing requirement files. None of them do the job.

[–] [email protected] 2 points 2 days ago (1 children)

The Python env has been trying this multiple tools approach for decades and consistently delivering a worse experience than languages that pack most things in one tool.

Rust is a bliss to use, largely thanks to cargo that takes care of build, dependencies, locking, tests, publishing etc. You say do one thing and do it well. In my experience they often do one thing in a mediocre way, while forcing users to understand which and how to combine dozens of possible tools in a development environment that keeps changing. It's messy, slow, error prone, and requires constant developer attention.

[–] [email protected] 1 points 1 day ago (1 children)

Most languages don't support packages containing multiple languages (C/C++, Cython, and Python). So Python situation is much more complex.

distutils

setuptools is complex

pip is complex

requirements files are complex

space aliens wrote pytest (and pluggy)

publishing and dependencies are super centralized, depending on pypi.org way too much.

Comparing Rust vs Python is nonsense. Rust is a stricter compiler on top of C. It has to deal with legacy C libraries. It has it very very easy.

[–] [email protected] 1 points 1 day ago (1 children)

and despite those differences, uv is essentially cargo for Python, showing it is possible.

[–] [email protected] 1 points 5 hours ago

Which begets the question, why inject an additional toolchain into package when not skilled at all in that toolchain. Can't support issues caused by that toolchain.