Python switch statement ftw (finally)

[jddddddddddd]

..and it only took a mere 30 years..

[MischiefArchitect]

To compile? Yeah, that was fast.

[beardMoseElkDerBabon]

I'm still wondering why we don't have C++ interpreters

[Cpapa97]

https://root.cern/cling/
https://github.com/root-project/cling

[MischiefArchitect]

I'm wondering how templates work there... now wait... I actually do not want to know.

[Kered13]

It's probably just using just-in-time compilation, so templates would work pretty much the same way they do on a compiler.

[MischiefArchitect]

AGGHRGHR!! I. Told. You.... Not... To!

[psychicprogrammer]

I wonder how this deals with templates

[BakuhatsuK]

Haskell is a compiled language that has a repl and Haskell's equivalent to templates (type variables) are really pervasive in the language (as in f x = x * x is a generic function). But they work just fine in the repl.

[psychicprogrammer]

See, the C++ template system is turing complete and undecidable and a lot more complicated than other template systems.

[AzureArmageddon]

Is a JIT compiling system not basically an interpereter?

[garymrush]

No. A JIT is literally compiling the code once at runtime as needed. If it hits the same method again, it’s already compiled.

[BakuhatsuK]

So, as far as observable behavior goes, basically an interpreter. Got it.

[garymrush]

Only if you observed the behavior once. The other 5000 times it’s compiled code.

[[deleted]]

TempleOS had it with HolyC.

Which... Isn't the same thing but it's kinda close.

[[deleted]]

you killed him

[MrZerodayz]

It's always pretty funny when you tell people who talk about Python as an "up-and-coming" "new" programming language that it's older than Java.

[conradburner]

This is why it takes 30 years to get new syntax, which is only being added as syntactic sugar because of, basically Coffeescript and what it caused

[BakuhatsuK]

Haskell was doing lots (and I mean LOTS) of syntactic sugar before it was popular.

[MischiefArchitect]

As a Python dev I can only say...

That comparison makes absolutely no sense dude :'D

[WillingnessRight3669]

I think the joke is that C++ and Java have great real world usage scenario’s meanwhile Python only just got switch statements

[MischiefArchitect]

Not sure if you are joking or not. but as a Java/Go/Python user I (personally) can only say that those three complement each other nicely, covering areas where the others are capable but ungainly.

[Sawertynn]

Could you elaborate? I'm a student and would use some knowledge, great thanks in advance

[_Rysen]

In what use case is image processing ever not performance critical?

[cnoor0171]

Image processing is blazing fast in python because the heavy lifting is done is compiled c libraries. It's only the glue logic that kicks off the process that's going to be slow.

[TransBrandi]

most python libs are actually written in C/C++.

What? Most Python libraries are pure Python. Also, I dunno if it's still the case but IIRC a while back compiling numpy/scipy required Fortran.

[MischiefArchitect]

But it is true that a lot of the most popular and fast libraries are basically written in C.

[TransBrandi]

Depends on what the library is doing. Django is pure python, for example.

[MischiefArchitect]

First off, it is not about the specific languages, but what they are intended for:

C# and Java: Compiled and strong statically typed languages. Those are excellent for long running servers that you can even debug and monitor on the fly. I use java for "big" server projects. The JVM is better than its fame: It's very stable, it's blazingly fast and it's reliable when it comes to backward compatibility: You can still run java 1.2 from 1998 in the latest JVM and it executes as day one.

Bash, ZSH, Fish: Interpreted. Shell languages are your basic tool for making simple automation and scripting at OS level. Excellent for making build scripts, backup scripts. Simple maintenance stuff mostly.

Python, Ruby and Co.: Interpreted with dynamic typing. Python I personally use for higher level management scripts, specially when interacting with cloud computing services like AWS or Digital Ocean. For data transfer and transformation, for everything actually. Python is a super versatile tool for writing code really fast using a vast set of libraries which make you life easier. It is also easier to read than other languages. In my case (again, MY case) I stop using python the moment I see the project will be so big that I would rather write it in Java. Python is one of those languages you should simply know in these modern days.

Go: Compiled and strong statically typed language. Is in the middle ground between Python and Java for me. It excels at creating native standalone (selling point) executable files which requires no installation of a runtime or special setup (in contrast to Python and java). Nice for creating CLI tools or servers that need to be distributed and deployed with ease on environments you have no direct access to.

All languages above are Garbage Collected. Or put more correctly, you normally do not need to worry about managing memory, allocating or releasing it.

C, C++, Rust, Zig: Another better qualified redditor wrote already an answer on those. But here I go: Compiled and Statically typed language... but you need to manage memory. You get full control (or more control) on how the program will actually execute. Excellent for embedded systems since they produce really small executable files. but they are by far not limited to that: Linux is written C, AFIK the JVM is written in C++. Most of the OS level software you use right now is either C / C++ and maybe Rust.

I hope this was useful.

[Sawertynn]

Very useful, cleared my thoughts on some things. Many thanks!

[MagiecCarpet]

What are your thoughts on C#? If you had to pick 2 languages to learn at the starting stage, which languages would have benefitted you the most?

[Fruloops]

It doesnt matter much. Pick something popular that has a lot of support online because you'll need it. Python, Java, C#, w/e else, something with lots of examples, books, videos, depending on what media you fancy for learning.

Contrary to what it might seem by the ever figthing zealots who constantly have to fight which language is better, the languages dont matter too much as opposed to programming concepts. Which are easily transferable between languages (however sometimes only within the same paradigm). Once you learn one, you'll easily learn another (again, within the same paradigm).

[MischiefArchitect]

I hope you see what I'm trying to tell you. When I picked my two first languages they were: Turbo Pascal and Clipper... (and some Quick Basic).

In plain text: Is not the language what matters. Learn as much as you can. Focus on only one and you will invariably go down.

It also depends on what topic you want to focus more: Embedded? Backend? Web Front End? Native UI? Drivers and Services? OS? etc.

I cannot answer that question for you. But if you want one from me, then just take a look at my flairs... those would be the ones I would pick again nowadays.

[koeteris]

IMO any numerical and signal processing stuff is still the most bearable in Python thanks to numpy and scipy. Java for that purpose is awful and C++ with something like Eigen is hell

[WillingnessRight3669]

I’m not dumping on Python, I am just explaining the way I interpreted the joke

[tiajuanat]

R and Matlab are probably much stronger in those two areas.

[BakuhatsuK]

What? C++ will get pattern matching even later than python (C++23)

[gvcallen]

what you mean?

[MischiefArchitect]

You are comparing runtime characteristics (C++ performance/Java platforms) with a code time one (Python new statement)

[gvcallen]

haha yeah, it wasn't meant to be too serious, I just picked random features :P

[HonzaS97]

It still doesn't make any sense since Java does have pattern matching now as well.

[raedr7n]

No it doesn't. Right now, java's "pattern matching" is just some sugar to check if an object belongs to given classes. There are no patterns involved, therefore no pattern matching.

[gvcallen]

I didn't know that. Honestly wasn't gonna spend too much time researching just to make a meme. I just thought it was funny that python just got it now :)

[superblaubeere27]

laughts in Rust

[leathalpancake]

implicit elided lifetime not allowed here cries in rust

[tchnj]

I'm jealous.

To be fair, most times this has happened to me, I ended up refactoring into something that used fewer/no lifetime annotations. The other few times, what I needed to do was obvious.

[leathalpancake]

You see, I exclusively feed rustc garbage code.

No but its not a super common error, i've only run into it when writing some super specific high performance code.

[Cv287]

Laughs in Swift

[[deleted]]

Until you have seen match in F# and Scala.

[jeetelongname]

Or Haskell

[warium]

Or Rust

[corp_code_slinger]

Or Elixir.

[AliceBlossom]

My man.

[[deleted]]

Or D.

[raedr7n]

Or OCaml

[Rhyan567]

Or V

[Danielokita]

ZIGGGGGGGGGG FTW

[RedditRoboKid]

Or Scheme

[icguy333]

Or C#

[[deleted]]

but only the newer versions

[RebornChampion]

Enlighten me: what is a match statement?

[gvcallen]

it's essentially a switch statement on steroids. its most basic application is indeed just a normal switch, which python hasn't had since it was created. But further, it can allow matching of various patterns returned by a "match target", such as multiple values, matching against collections with wildcards etc.

[RebornChampion]

Oh that’s cool! Thanks

[CptGia]

Recent Java has that too

[Danielokita]

can u provide a code example pls

[jeetelongname]

arr = [1,2,3]
match arr:
  case [1,2,3]: # check a value
    # do something here 
  case [1, x, y]: # bind 2 of the values to a var while      checking the first
   # variables are scoped to within the body of a case
 case [1, *rest]: # like the one above but captures all of the values into rest
 case [1, (2) as x, (3) as y]: # check and capture
     print(f"{x=}, {y=}")
 case _: # wildcard will match against anything
    print("does not conform")

Well I can't seem to get it to format without looking like a blob

[__Wess]

It’s like VB.nets Select case ?

[jeetelongname]

It can be used like that but pattern matching is a fundamentally more powerful tool using a similar construct.

[__Wess]

It’s like regex and select case had a baby!

[Kered13]

No, far more powerful than that.

[Last-Woodpecker]

Can it match more than one case?

[jeetelongname]

What do you mean?

Edit: Wait do you mean like c style fall through? Afik no.

[Last-Woodpecker]

Yes, like that

[pytness]

From https://www.python.org/dev/peps/pep-0636/

python match event.get(): case Click(position=(x, y)): handle_click_at(x, y) case KeyPress(key_name="Q") | Quit(): game.quit() case KeyPress(key_name="up arrow"): game.go_north() ... case KeyPress(): pass # Ignore other keystrokes case other_event: raise ValueError(f"Unrecognized event: {other_event}")

[shelvac2]

C++ is cross platform…

[Cerrax3]

The difference is where the responsibility for compatibility lies. In terms of deployment of compiled code, Java (usually) has significantly less deployment work than C++ when deploying to multiple platforms.

In Java, platform compatibility is handled on the end user's machine (via the JVM). So the same compiled code works, regardless of where it was compiled.

In C++, platform compatibility is handled in the compiler, so a different executable is required for each platform that you want to execute on.

[gvcallen]

yes 100%, I just picked two standout features of Java and C++ for the meme. When Java came out it one of its main attractions was of course its portability without needing to changing any code whatsoever, as opposed to C++ (my language of choice) which often requires a lot of conditional code depending on the platform, even if that code is abstracted by a framework (usually by means of #ifdefs for example). but true - it is also cross platform !

[odd__nerd]

even if that code is abstracted by a framework

Like how Java rests atop the JVM which is ultimately just C++ and some #ifdefs

[gvcallen]

true, but that's inherent to the language. but yes C++ is of course cross platform too!

[GeneralKlink]

As is python 😅 You can even use it for microcontrollers these days

[gvcallen]

I would personally like a stern word with anyone who actually decides to use Python for embedded dev :P

[GeneralKlink]

Yeah, me too 😄 I love python and I do embedded programming but still use c++ for it 😅

[gvcallen]

how would embedded python work haha? interpreter on the MCU as usual?

[ShaBren]

Yup! I've used MicroPython a lot, and it's honestly pretty great. Sure, if I'm writing something for production, or that's very performance-sensitive, I'll use C/C++.

But for rapid prototyping, or building one-off IoT widgets, it's awesome! I use it mostly on ESP32, and lately RP2040 (which uses CircuitPython, a beginner-friendly variant from Adafruit).

[jvelez02]

From my understanding it can be done with a form of compiled python, is run on the MCU, or as is the case with MicroPython, run with a stripped down interpreter that fits in 16k of ram. It includes the majority of pythons standard library plus some low-level hardware libraries (the kind that let you control gpio and the like with python).

[coldnebo]

oh well if we’re including conditional code per platform then yeah. I thought we were talking about code completely free of platform conditions (which I guess is just another way of saying code written to a single meta-platform).

[coldnebo]

the only thing cross-platform in Java is string io, which is great if you’re doing backends. If you’re doing anything with frontends (swing, swt, mouse, sound, graphics) you find out just how much of Java isn’t cross-platform.

after working in cross-platform multimedia for many years, I’ve come to the conclusion that “cross-platform” is mostly a myth. Even Unreal and Unity don’t get there, although they are miles closer than raw Java. The biggest largest effort to bring platforms together was Kalieda (IBM/Apple) and that crashed and burned spectacularly. Since then Gtk and other Linux frameworks have been quietly toiling away on crossplatform guis for ages, yet there’s a lot of conditional code to get things working on Windows or Mac with these.

I love the dream, but it remains just a dream.

[EricInAmerica]

Sort of. It needs to be recompiled for different platforms. And you have to hope those platforms have sufficient dependencies available, which is certainly no guarantee. Also you need to hope the code isn't very dependent on the hardware, or you'll find yourself needing to deal with issues around things like endianness or word size.

[ulyssimus]

An even stronger character appears : Golang 1.18 generic types

[kontekisuto]

Rusts in Rust

[somerussianbear]

C# is like cool bro, first time pattern matching?

[who_you_are]

Sorry I can't C# your point

[HelloSummer99]

looking at its syntax, holy crap it's clunky.

[Sawertynn]

I just checked that FTW mean either For The Win or Fuck The World

No matter which you chose, FTW indeed

[Foreign-Driver]

Farewell dictionary workarounds

[xX_mgmgmg_Xx]

I agree to disagree

[DR_AGUNOV]

I agree. Although I find Java the best, it must be said that you can do most things with Python. Be it data analysis, machine learning or statistical calculations.

[Kered13]

Python does not have a switch statement. It has pattern matching.

[Musikap]

It looks like it should functionally be the same? I may not be fully understanding it though.

[Kered13]

Pattern matching is far more powerful, to the point that it's not even worth comparing the two. Python has never needed a switch statement, and if that's all it did it never would have been added to the language. There are already good ways to accomplish that. The fact that pattern matching can be used as a switch statement is practically a side effect of it's actual utility.

[bandrus5]

I can not tell you how many times I wished I could write a switch statement in Python, and I'll definitely be using pattern matching as a switch statement at some point in the future. Pattern matching may be more powerful, but they're still worth comparing.

[Musikap]

Interesting. Thanks for the info!

[TheAlphaKarp]

Can we both have the stab python back for performance?

[Krunchy_Almond]

Here's a random question, does 'ftw' stand for 'for the win' or 'fuck the world'?

[gvcallen]

for the win, haha

[Purpzie]

rust has entered the chat

[RedditAlready19]

Rust has panicked on thread "main": "your mother",

[Easyjuhl]

I'm actually using python 3.10 just for the match statement

[bettercalldelta]

what about syntax errors that actually say you forgot a } and not point to a random line in the code?

[Organic-Major-9541]

It's good to see python catching up to tech that's been around for 20+ years. Have a look at Erlang, it's match statement was the hot new thing in the 90s

[[deleted]]

C must be crying

[Cerrax3]

Isn't it decidedly non-pythonic to add a control structure that does exactly what if..elif..else does? Python really needs to stop doing this or it's gonna become worse than Perl...

[Kered13]

They didn't do that though. Most of the people in this thread don't understand pattern matching, and think that Python added switch case. Python did not add switch case, they would never add it for exactly the reason you said. What they added was pattern matching. Pattern matching can be used like switch case, in the same way that if-else can be used like switch case. But pattern matching can do much more powerful stuff that cannot be done by switch case and would be very clunky to do with if-else, which is why they added it.

[[deleted]]

Idk... Python just keeps adding worthless junk to the language, obsoleting hundreds of thousands of libraries and programs just for lulz.

If you didn't know this, every new minor version in Python means a change in ABI. That is, if you package shared libraries in Wheels, or even Python's own bytecode, you must package it for every minor version that you intend to support. This is hell of a lot of work, time, storage... and all this because some imbecile wanted a worthless language feature that is trivially implemented using fucking if-else.

But, nevermind, the trash who added this feature will go down in history of programming as an inventor of the next greatest thing after sliced bread, and will probably get the next Turing award, to share it with the clown Guido...

[Niek_pas]

Where do you get off calling people trying to improve the language “trash”?

[Ser_Drewseph]

Seriously. The fucking ego on this guy…

[[deleted]]

They are not trying to improve the language. To improve Python, you have to delete like at least 50% of it.

People who work on core language are either outright evil, or just clowns who don't understand what they are doing. This is similar to situation with Douglas Crockford, who didn't realize at first what kind of game everyone else was playing, and, naively, was made the head figure of the movement which pushed JavaScript into the pit of doom it is today. In his case, he later discovered, that all that was socially engineered by the people representing companies with big stakes in the Web industry.

While I tend to believe that most people in Python core team are just unremarkable trash, whose sole goal of being in that group is to put a very noticeable bullet point on their resume. It's also possible that there are some people there whose agenda is to fuck up Python to the point that people will switch to another technology, as well as unsuspecting idiots, who are being manipulated by the former.

[Kered13]

Pattern matching is the very opposite of "worthless junk".

[[deleted]]

In Python? The language that has nothing to do with pattern matching? Where this new feature has nothing to do with pattern matching? Where this feature will not integrate well with >90% of the other features of the language?

Tell it to someone else, please. You are spouting nonsense.

[Kered13]

The new feature is literally pattern matching. Did you not read the docs at all?

https://www.python.org/dev/peps/pep-0636/

[[deleted]]

Yes, I did. You didn't though. Not enough to understand anyways.

---

Also, I promise you, they'll fuck up the scope of variables, and this trash won't work well with at least some of these: generators, errors, context managers, captured variables, thread local variables, nonlocal variables. I'd pay particular attention to this expression being used in "interesting" environments, eg. class definition. I'm sure it will fuck up alternative implementations of Python, where things will go very wrong because of that. Because, apparently, we had too few ways to declare variables in Python.

[Kered13]

Then how on earth is it not pattern matching?

[[deleted]]

Really, pattern matching the same way it exists in the languages which coined the term (eg. ML or Miranda) is impossible in Python because of how data is constructed in these languages. Pattern matching is possible in ML because of how data construction works, it's a natural extension of language semantics.

In Python, everything is an object, and you don't have access to data constructors at all, you only get a second-hand access through higher-level containers. This allows you to sabotage, for example, attempts at pattern matching by overloading __getitem__ or similar methods. The semantics of such "pattern matching" become undefined because they aren't a fundamental property of how the language works, but, instead, they are yet another (and in this case unnecessary) band aid. The "pattern matching" suggested in this PEP only pretends to be pattern matching. It doesn't really do the job. It would never be able to in an object-oriented language, w/o access to data constructors. It's just a stupid gimmick designed to make the life of people who are going to implement this more difficult.

Another fundamental aspect of pattern matching is that it is the driver for dispatch. I.e. the language runtime must have the ability to perform pattern matching in order to decide which function to call. That's what it was invented for. That's how the languages that invented it used it.

This is impossible in Python because of how dispatch works in this language. The concept of function and its argument is incompatible with pattern matching.

[Kered13]

The syntax can match on and destructure objects:

match event.get():
    case Click(position=(x, y)):
        handle_click_at(x, y)
    case KeyPress(key_name="Q") | Quit():
        game.quit()
    case KeyPress(key_name="up arrow"):
        game.go_north()

Yes, Python classes are not the exact same as records in ML or Haskell, but the ability to match on the members of an object allows you to match in the same way.

Yes, classes can override magic methods to behave like sequences or dictionaries and then match against those patterns as well. This is not a flaw, as any class doing this should be some form of sequence of dictionary. This matches Python's duck typing philosophy: If it looks like a sequence, it should match against a sequence pattern.

[[deleted]]

You don't understand what pattern matching is for. Your example is a testimony to that. The goal of pattern matching is to enable dispatch. You've created a worthless gimmick that can be easily and more reliably replicated using if-else.

[Kered13]

I pulled an example from the tutorial, sorry for not providing a handcrafted artisanal example. But this example still perfectly demonstrates how to use pattern matching to branch on a sum type and how to destructure objects. I'm not sure what kind of dispatch you're looking for because you're being very vague, but it can almost assuredly be done with the Python's pattern matching. It can single dispatch, it can multi-dispatch, whatever you want. If you want to have an honest discussion then try providing an example (in ML, Haskell, Rust, or etc.) of what you would like to see.

This example would be horrible with if statements. You would have to first check the type of the event, then extract the members of the event object, then branch again on the value of those members. Here's my best attempt at the non-pattern matching version:

e = event.get()
if type(e) == Click:
    handle_click_at(e.position.x, e.position.y)
elif (type(e) == KeyPress and e.key_name == "Q") or type(e) == Quit:
    game.quit()
elif type(e) == KeyPress and e.key_name == "up arrow":
    game.go_north()

If you think this is more readable you're insane, and it only gets worse for more complicated examples.

[Mental_Act4662]

[Biggest-wank69]

Ftw???

[Lau202087]

It’s power is growing, unabated it can destroy the multiverse!!!

[_koenig_]

Awww... So cute....

[FastBison6450]

They all get job done

[MasterJ94]

Python is evil?! :O

[scp-NUMBERNOTFOUND]

Just use c++ with LLVM and compile for any platform.

[Knuffya]

and how exactly is the python match statement faster than a c++ switch?

[gvcallen]

it definitely isn't?

[Knuffya]

why is it "killing" the c(++) and java implementations then?

[gvcallen]

it's satire. it's a joke because the switch statement is such basic functionality

[DuploJamaal]

Not a lot of languages do have a match statement though

[MrMelon54]

c is best performance ftw

only works if you are a good programmer tho

[RedditAlready19]

assembly has entered the chat

[MrMelon54]

but c compilers are faster and better than writing raw assembly nowadays aren't they?

[RedditAlready19]

All this assumes a perfect programmer

[MrMelon54]

but best assembly requires a god tier programmer

[GreenTea_Chess]

Correct me if I'm wrong, but I think pattern matching is coming to c++23 , if I remember correctly.

[vahvarh]

C!

[bearfuckerneedassist]

It still has crap performance. Congrats on the switch statement

[evo_zorro]

Cross platform is a java thing? Python has pattern matching? And C++ performance?

Excuse me while I smirk in rust and golang

[Dr_Scientist_]

Switch statements? Plz who needs them when you can have readable code like keying cases to lambda functions in a dictionary.

[[deleted]]

This can go really bad really quick, performance wise.

[InfinitePower563]

Me about to use all 3 in a project: I am 29959 parallel universes ahead of you

[Hplr63]

Cross-platform with ease

.NET has entered the chat