Comment by zahlman

Generally you have the right of it, but a word of caution for Pythonistas:

> The point is still different. In PyPI, if I put `requests` in my requirements.txt, and I run `pip install -r requirements.txt` every time I do `make build`, I will still only get one version of requests - the latest available the first time I installed it.

Only because your `make build` is a custom process that doesn't use build isolation and relies on manually invoking pip in an existing environment.

Ecosystem standard build tools (including pip itself, using `pip wheel` — which really isn't meant for distribution, but some people seem to use it anyway) default to setting up a new virtual environment to build your code (and also for each transitive dependency that requires building — to make sure that your dependencies' build tools aren't mutually incompatible, or broken by other things in the envrionment). They will read `requests` from `[project.dependencies]` in your pyproject.toml file and dump the latest version in that new environment, unless you use tool-specific configuration (or of course a better specification in pyproject.toml) to prevent that. And if your dependencies were only available as sdists, the build tool would even automatically, recursively attempt to build those, potentially running arbitrary code from the package in the process.