If I write a shell script looking something like:

  #!/bin/sh
  exec rg $@

Then I did not actually write ripgrep in pure shell.

"Pure Python" ultimately means that it all runs within the python interpreter, with no dependencies on code that runs outside of the interpreter (standard library notwithstanding).

When people say "pure X", to me, it normally means they didn't involve an FFI or external compiler. This is an often beneficial thing (though also often at the expense of performance and maybe correctness) since it simplifies your build process.

For example, here [0] is a "pure Python postgres driver" and the implication is that it doesn't use libpg.

Or see also this discussion [1].

I don't mean that the author should or shouldn't do whatever they want. I just wouldn't use the term "pure" here or even say this is an engine written in Python since a large chunk of it is not written in Python. That doesn't mean this is not a cool project. It's a cool project!

[0] https://github.com/tlocke/pg8000

[1] https://www.reddit.com/r/learnpython/comments/nktut1/eli5_th...

Pure-python commonly is used to refer to code that has no external dependencies.