How the Python import system works

Post by zarzavat » Sun, Jul 25, 2021, 11:10 PM UTC

BossingAround wrote: post #187

zarzavat wrote: post #141

Earlier quoted context omitted.

In JS land everything is a relative import. It's nice because you can move a whole directory of code from one project to another (or around in the same project) and it still works because all the imports pointing to other files inside that directory were relative, you only have to fix imports that go outside the directory. Also the way that JS imports are just relative paths is very nice because it means that the imp…

> It's nice because you can move a whole directory of code from one project to another (or around in the same project) and it still works Yes, just like absolute imports... > relative paths is very nice because it means that the imports are statically determinable, your editor can understand them and fix them automatically and you can trust that refactoring 1) Just like absolute imports? 2) I absolutely contest that…

    import a.b.c
    sys.path.insert(0, 'some/other/path')
    import x.y.z

    env PYTHONPATH="foo/bar:$PYTHONPATH" python ...

    import c from "./a/b/c"

Post by chucke » Mon, Jul 26, 2021, 12:46 AM UTC

andrewaylett wrote: post #138

sillysaurusx wrote: post #27

Fun fact: you can overload the Python import system to work with other languages that you create . I use this for my Python-based Lisp: https://github.com/shawwn/pymen/blob/ml/importer.py import foo checks for "foo.l", and if found, compiles it to foo.py on the fly and imports that instead. It's so cursed. I love it.

Lots of things you can do with Python but probably shouldn't and people typically don't. That's one reason I prefer it to Ruby, or even Node, where monkey-patching or otherwise exposing bad magical behaviours is common and even encouraged -- the power is all there, but the ecosystem encourages you to use it for good, not evil. This sounds very much like the good kind of magic, though.

Post by kortex » Mon, Jul 26, 2021, 1:07 AM UTC

pnt12 wrote: post #186

awestroke wrote: post #36

Earlier quoted context omitted.

I disagree. I find it hard to get started in python. There are loads of package managers, so I don't know which one to pick. There are multiple different rules for for how imports work with local files. The standard library is full of of functions that one should not use any more, and you need to know which is which. Defining a main entrypoint consists of checking a magic __NAME__ constant. You have internalised all…

Counterpoints: Start with pip, the official package manager. You don't have to start with virtual envs: I didn't. I haven't ran into any function which I "should not use". You don't need an entry point, you can just write code in a file. Besides that, I don't see how much it differs from other languages with implicit entry points, where you need to match a certain name in your function. Imports: yes, those are annoyi…

Post by drathier » Mon, Jul 26, 2021, 8:39 AM UTC

jnwatson wrote: post #167

neoncontrails wrote: post #160

Earlier quoted context omitted.

That stackoverflow library is so gloriously bonkers. Is it useful in practice?

No. Perhaps for a hackathon.

Post by matheusmoreira » Mon, Jul 26, 2021, 11:32 PM UTC

brundolf wrote: post #29

matheusmoreira wrote: post #24

It's certainly a lot better than Ruby's require which just executes code and alters global virtual machine state. Not too different from C's #include. My favorite is Javascript's. Modules are objects containing functions and data, require returns such objects. Simple, elegant. Completely reifies the behind-the-scenes complexity of Python's import, making it easily understandable.

Though that's not how JS's new module system works, which I would say is also elegant in its own ways, but juggling two different systems is less so