I'm just grateful I'm not a core Python dev after reading this thread. I've never seen so much negativity concentrated in one place in quite some time, for a feature of a programming language which is fairly innocuous.
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How the Python import system works
61–70 of 209 posts
Re: How the Python import system works
#62Fun 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.
Wait, what? > that you create As in existing language supplied eg. Perl, Java, etc., or literally anything? Like bootstrapping your own home made language from scratch?
Literally anything. 'Tis a homemade homegrown lisp, grown by Scott Bell for several years till I took it all for myself. Nom nom.
It starts with reader.l: https://github.com/shawwn/pymen/blob/ml/reader.l where the raw character stream is turned into a bunch of nested arrays. E.g. (+ 1 2) becomes ["+", 1, 2]
Then it's punted over to compiler.l https://github.com/shawwn/pymen/blob/ml/compiler.l where it's passed through `expand`, which does a `macroexpand` followed by a `lower`. E.g. (do (do (do (print 'hi)))) becomes ["print", "\"hi\""]
Then the final thing is thrown to the compile function, which spits out print("hi") -- the final valid Python code that gets passed into the standard python `exec` function.
Works with all the standard python things, like async functions and `with` contexts. Been screwing around with it for a few years.
Re: How the Python import system works
#63Earlier quoted context omitted.
> three modules cannot depend on each other in a circular way What would the purpose of circular modules like this be? You may as well collapse into a single module and the situation would not be any different would it?
The purpose is you want to use code in other modules. If you keep doing that for a while, a circular dependency will happen. This is the dumbest thing thing in Python. All other languages I know have solved it.
> The purpose is you want to use code in other modules.
So put them in the same module? Circular modules don’t give you the benefits of modules, do they? Not an expert in modularity.
Re: How the Python import system works
#64This is so needed. I feel like a lot of people know enough about python imports, but everyone has pains with it.
Re: How the Python import system works
#65But despite being terrible the Python import system is remarkably easy to get started in. And generally easy for beginners to work with (put all the code in the same folder or "pip install"). There are some lessons here that other languages would do well to learn. Trouble importing 3rd party libraries must be a kiss of death for beginner engagement.
No. Python is a language I have to use infrequently, but I give up half of the time using a project found on GitHub because of missing depencies, the need to install a package manager to install another package manager to install dependencies, etc. The other day I spent some times fixing a docker image that was working fine few months ago but which was now failing because some Python package install returned an error.
On the contrary, C projects tends to build with 3 commands and C# (often way bigger) with a single command, and without having to do magic things around "virtual environments".
Re: How the Python import system works
#66Fun 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.
Can I just say that the introduction to Lisp you made in your README.md is really good!
I keep trying to get into Lisp (and JavaScript, and TypeScript, etc etc) but I've been a sysadmin my whole professional life and also a chronic pain sufferer. That translates into mostly having energy only for work and that's it, not much motivation to learn after work or on the weekend.
In my DevOps job, I write Terraform, plus read javascript and cloudformation yaml. I do wish I could convert my current stuff to AWS CDK, but I don't want to fragment the multiple projects that are using Terraform. (I haven't looked into tf-cdk much at all yet)
Re: How the Python import system works
#67There are two things that are annoying about Python's import system. Number one is that relative imports are weird. My intuition about imports is good enough that I never bothered to learn all the rules explicitly, but sometimes something simple is just not possible and it bites me. I think the case is importing files relative to a script (and not running with python -m ...). Number two is, in order to do package man…
> Number two is, in order to do package management, you have to create a fake python installation and bend PYTHONPATH.
If I understand what you mean by package management in this context, I wonder if editable installs will help you.
https://www.python.org/dev/peps/pep-0660/#abstract
https://discuss.python.org/t/pronouncement-on-peps-660-and-6...
Re: How the Python import system works
#68Earlier quoted context omitted.
Wait, what? > that you create As in existing language supplied eg. Perl, Java, etc., or literally anything? Like bootstrapping your own home made language from scratch?
Literally anything. 'Tis a homemade homegrown lisp, grown by Scott Bell for several years till I took it all for myself. Nom nom. It starts with reader.l: https://github.com/shawwn/pymen/blob/ml/reader.l where the raw character stream is turned into a bunch of nested arrays. E.g. (+ 1 2) becomes ["+", 1, 2] Then it's punted over to compiler.l https://github.com/shawwn/pymen/blob/ml/compiler.l where it's passed throug…
That's absolutely disgusting. But in a Web Assembly sort of way... I don't know whether to spit on it or give it a medal.
Re: How the Python import system works
#69Earlier quoted context omitted.
What would the purpose of circular modules like this be? You may as well collapse into a single module and the situation would not be any different would it? What is the purpose of modules? You may as well collapse into a single script and the situation would not be any different, would it? I'm not being facetious here. The answer to the second is the answer to the first. A common example might go like this. You have…
> What is the purpose of modules? So parts of the system can be managed independently. > The answer to the second is the answer to the first. Clearly not - since circular modules cannot be managed independently!
To me the purpose of models is to help humans manage code. Our brains don't hold much at once, so the more we can forget about in a given circumstance, the easier it is. So I think btilly is correct: the reason I want modules, ignoring things I don't care about, is the same reason I want them to deal reasonably with circular references.
Re: How the Python import system works
#70I've been programming in Python professionally for more than five years. I consider myself quite a good programmer. I still don't have good grasp on Python's import system. Does anyone else have similar experience?
Same. Occasionally I will get into some sort of mess, learn how it works under the hood enough to get myself out, and the promptly forget everything.
And I think that's for the best. I'd much rather have a happy path that I stay on than use some sort of dark magic that nobody who comes after me will understand.