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Comment by leontrolski | Hacker News Reader

A really nice collection of examples in their original and their refactored form - nice work. I'm similarly in two minds about the feature, it's cute, but is it worth it?

I think it's indicative that the nicest use is in AST processing. As someone that works on the occasional parser-y side project it looks pretty cool, but also, 97% of professional Python development is in data-science/application development. I suspect this is a case of the core language devs having a bias towards features that are useful to them as opposed to the community as a whole.

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> but also, 97% of professional Python development is in data-science/application developmen

No. There is not a single field with " 97% of professional Python development". As a freelancer, I see python used for everything, everywhere. From education, to math, to biology, to geography, to web dev, to automation, to testing, to desktop app...

Thanks! Yeah, that's how it seemed to me too. The AST processing examples really sell it. But the fact that Warehouse is a sizeable application (60kLoC) but didn't really have any good uses for pattern matching is telling.

Pattern matching enable an entirely new class of features that are too tedious and error prone to implement otherwise. Specifically, anything that has to do with recursive structures. Are recursive structures useful? Perhaps, given that natural language is fundamentally based on recursive structures.

Apps designed pre ubiqutous pattern matching say little about whether pattern matching has good uses or not. More likely features alluding to pattern matching were culled early in the design process.

I think it's a bit of a stretch to say that "anything that has to do with recursive structures" is too tedious to implement with without pattern matching. I've written my share of recursion in Python, and have written a number of recursive parsers and language interpreters in Go (which also doesn't have pattern matching). I didn't find it bad at all.

That said, I think your overall point is interesting. Will this new feature in Python mean that Python is used for certain domains it wasn't previously? I have my doubts, partly because it's a fairly slow byte-code interpreted language, and that limits its usefulness (I've seen a number of compilers written in OCaml, for example, which has pattern matching, but is also fast).

I'd say it's a good thing people don't try to use the feature in a context it's not useful. Don't use the shiny new toy just to play.

Python has to cater to a vast crowd, and geographers don't have the same needs as data scientists, web devs, 3D artists or sysadmin.

So it's logical some tools will be useful in some cases, and not some others.

Amusingly yesterday I was doing something in JS, and though, "ah, I wish I has this new PM feature from python there".

The day before, I had to deal with pedantic exception, and wish I had a pattern matching to make a case depending of the number of errors and their message. I had to do a hacky loop for something that had to do with structure, not repetition.

Just like the walrus, I don't think it's something that will pop up everywhere, all the time. But when it is useful, it will make the code nicer.

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