[chippiewill]

In this day and age you don't usually have to download the packages to resolve the dependencies as PyPI can usually expose it (unless you need to install from sdist which is less common these days).

Dependency resolution is slow because it's computationally very expensive. Because uv is written in Rust the resolution is just much much faster. IIRC they actually reuse the same resolution package that Cargo (Rust's package manager) uses.

[bsdz]

Yes I think I heard pypi started exposing dependency info so it makes sense to use that where possible.

The dependency resolution computation is an interesting problem. I think poetry at some point switched to mypyc for compilation (although I can't find conclusive evidence for it now). From my experience, mypyc doesn't really improve performance much compared to say writing a c/c++ extension. Perhaps offloading dependency resolution in poetry to a native c library is a way to match uv.