constraint vs requirement. What's the difference? (programming.dev)

submitted 1 month ago* (last edited 1 month ago) by logging_strict@programming.dev to c/python@programming.dev

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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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[-] logging_strict@programming.dev 2 points 1 month ago* (last edited 1 month ago)

my position is it's not messy enough

Lets start off by admitting what the goal is.

We all want to avoid dependency hell.

Our primary interest is not merely cleaning up the mess of requirements files.

Cleaning up the mess results in some unintended consequences:

noise
complexity
confusion

noise

All the requirements information is in one place. Sounds great until want to tackle and document very specific issues.

Like when Sphinx dropped support for py39, myst-parser restricted the Sphinx upper bound version, fixed it in a commit, but did not create a release.

Or cffi, every single commit just blows our mind. Adding support for things we all want. So want to set a lower bound cffi version.

My point being, these are all specific issues and should be dealt with separately. And when it's no longer relevant, know exactly what to remove. Zero noise.

complexity

When things go horribly wrong, the wrapper gets in the way. So now have to deal with both the wrapper and the issue. So there is both a learning curve, an API interface, and increased required know how.

The simple answer here is, do not do that.

confusion

When a dependency hell issue arises, have to deal with that and find ourselves drawn to poetry or uv documentation. The issue has nothing to do with either. But we are looking towards them to see how others solve it, in the poetry or uv way.

The only know-how that should be needed is whats in the pip docs.

Whats ur suggestion?

Would prefer to deal with dependency hell before it happens. To do this, the requirements files are broken up, so they are easier to deal with.

Centralizing everything into pyproject.toml does the opposite.

Rather than dealing with the issue beforehand, get to deal with it good and hard afterwards.