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Comment by YPCrumble | Hacker News Reader

I understand the value of a locking mechanism in the JS ecosystem because 1/ many packages depend on an intricate web of other packages that overlap, 2/ many packages use semver ranges, and 3/ you don't want two versions of the same package running on a user's browser, due to conflicts and increased size.

I can't think of many Python packages that have the same issues, and Python code isn't sent to and running on a user's browser.

Am I wrong or is there a reason that a locking mechanism (other than git) is helpful in Python?

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I think this has less to do with "you don't want two versions of the same package running on a user's browser" and more to do with "when I clone a project and run npm/pip install I want it to be in a known state".

I don't use Python/pip much but as for npm: the problem is when your dependencies, direct or indirect (dependencies of dependencies), aren't "exact". You have something like "~1.2.3" or "^1.2.3". If every developer followed Semvar perfectly, never shipped regressions or new bugs when fixing a bug, and was always able to identify every breaking change then life would be perfect.

That is, however, not the world we live in. So a "lock" file respects your "fuzzy" versions ^/~ when you first run the npm install and then subsequent runs will install using the exact versions you downloaded the first time. This helps solve the "works me me"/"work on my machine" problems. The idea being if you can run it locally then the build server and production can also build/run your code.

All of those apply to Python as well except the multiple packages concern has nothing to do with a browser and everything to do with the fact that a given Python process can only load one version of a library at a time (and probably for good reason).

I mean, Rust uses the same locking mechanism to great success. I've never seen a breaking change from upgrading a Rust dependency that preserves semver (which is 99% of them)

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