typing VS mamba

Iterable[str] is unfortunately evil as it matches str which is often unintended. (see: https://github.com/python/typing/issues/256) One would need both NOT-type and AND-type in order to properly handle these.

The basic motivation behind them is that functions can have arguments that can only take a specific set of values, and those functions return values/types change based on that input. Common examples are (you can find more here):

While yes 26 people liked the idea here: https://github.com/python/typing/issues/193

but looking at relevant issues on GitHub it seems this has been shot down repeatedly. python/typing#18, python/typing#213

See https://github.com/python/typing/issues/256 for a discussion.

Lower bounds are not supported for TypeVars, unfortunately.

Mypy allows that because initial versions of PEP-484 allowed that. This has changed; here's the current wording on the PEP:

> This is no longer the recommended behavior. Type checkers should move towards requiring the optional type to be made explicit.

https://www.python.org/dev/peps/pep-0484/#id29

Dunno, other, larger projects than the one I'm working on seem to run up against this from time to time. (rasa_core, to pick one example from near the top of a Google search; also Telethon, Blender, TensorFlow, Pandas. Guido also filed a bug on the typing module in an early version of Python 3.5 because of unexpected implications of this particular issue, so the problem isn't exactly purely theoretical.) That's aside from the wish for conceptual purity in the call signatures of classes and their subclasses, which is not always and automatically a bad wish to have; and the notion that a language that prides itself on its introspective faculties might want to make introspection of classes from the top of a class hierarchy possible, at least in theory? Perhaps to facility learning about the language and/or visualizing large class hierarchies easily, for instance?

>"everyone" seems to know Mamba. I never heard of Mamba

Only the "everybody who knows what mamba is" are the ones upvoting and commenting. Think of all the people who ignore it. For me, Mamba is the faster version of Conda [1], and that's why I clicked on the article.

https://github.com/mamba-org/mamba

Yes, this is a big disadvantage. But have you tried Mamba that aims at implementing Anaconda more efficiently? It works really well in most cases.

https://mamba.readthedocs.io/

Because conda is very slow at resolving dependencies. Mamba (https://github.com/mamba-org/mamba) is faster if that is your goal

use mamba instead

We started using tl::expected in https://github.com/mamba-org/mamba/ since the beginning of this year and some other related projects like https://github.com/mamba-org/powerloader . I don't know much other big open-source codebases that use that specific lib.

Great writeup. Minor comment about the portion of the post mentioning Conda being glacially slow: Mamba [1] is a much better drop-in replacement written in C++. Not only is it significantly faster, but error messages are much more sane and helpful.

That being said, I do agree that Pkg.jl is much more sleek and modern than Conda/Mamba.

[1]: https://github.com/mamba-org/mamba

I thought that python could live a little longer when I learned about mamba. But then I found out it is written in C++? Why write a package manager for a dying language in a language that is almost dead???

Yes, I use Conda enviroments (actually I use Mamba to manage them now).