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Particularly interesting comment by ddelange on resolving Python packaging version complexity issues using pip's constraints functionality.

From: pypa/pip#9187 (comment)

could there be an easy option that forbides pip-21.2.1 to downgrade any already installed package (like specifying the existing packages version as a minimal constraint >= ) ?

@stonebig if you still have your pip cache populated, there is a way to achieve it without spamming the pypi registry: you can use the output of pip freeze and feed it to your pip command with an additional -r (it can be used multiple times):

pip freeze | sed 's/==/>=/' >> ./constraints.txt
pip install <some-new-package> -r ./constraints.txt

As all of constraints.txt is already satisfied, nothing will be re-installed unless needed. And given a populated pip cache, it also wont consume much bandwidth.

Whether it actually speeds things up (or causes panic instead), I don't know.

If you want to be even more strict (don't down NOR upgrade anything in your env), you can leave out the sed replace above and use pip's --constraint flag instead of -r. Constraints passed here will not be installed (the file can contain any set of packages also unrelated to your install), but it will force conflicts faster.

Hope that helps!

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