Comment by bob1029 | Hacker News Reader

Comment by bob1029 | Hacker News Reader

I just took a look at this and I am confused as to the actual practical utility of pattern matching in a language that is not strongly-typed to begin with.

My initial take upon stumbling upon the controversy was "why would pattern matching be bad?" because I have only experienced it through the lens of C# 9.0. Upon reviewing PEP 622 and looking at some examples of usage... I am in agreement with the detractors. This just doesn't seem to make sense for python, but I would certainly hate to get in the way of someone's particular use case as long as the new feature doesn't fundamentally cripple the language for others.

IMO, Microsoft nailed it with their pattern matching implementation:

https://docs.microsoft.com/en-us/dotnet/csharp/pattern-match...

Python is strongly-typed. With its built-in type annotation syntax and a checker like mypy or pyright, it is statically-typed, too.

My experience with mypy has been pretty negative.

Not because mypy is bad per se, but it just doesn't flow into a Python workflow naturally. Every time you try to interact with an external module without these annotations you immediately lose all the advantages of statically typed programs.

For me, Python with annotations just doesn't make sense, at that point I would prefer to program in Rust or Java.

For external modules, you can generate stub files that contain inferred and/or manually supplied annotations[0].

[0] https://mypy.readthedocs.io/en/stable/stubgen.html

A bonus for writing strongly typed code and using a small/safe subset of python is that you can transpile it to languages like rust or kotlin

Type annotation and mypy, while better than nothing, is a hack and doesn't always properly work so in a real codebase you'd be using `# type: ignore` quite often even if all of your downstream code is properly type-annotated and mypy-typechecked.

Most importantly though, it does not make Python statically typed, by no means. It just lets you lint stuff in a semantic fashion (which is helpful, no doubt), improves auto-completion and removes the need of listing type requirements in docstrings.

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