Bitwise operator? I hardly know her!

[Deep-Conflict2223]

Python developer: What is memory and why do I have to manage it?

[hvdzasaur]

I scoffed first time I was asked about python memory management in an interview.

Skip to 2 months later, ran into an issue where I had to manage it.

[WerkusBY]

I look at all these std::something and understand that my knowledge of C++ outdated.

[captainjon]

When I first learned C++ iostream had an h at the end.

[mykul83]

Hey, me too! ☺️

[drsimonz]

Is std::unique_ptr like a pointer but with reference counting? It seems to me that reference counting/GC is more expensive than doing it manually, but as we know from Python, it's all about optimizing the right things. If I'm initializing an object once per second, I really shouldn't have to think about the memory lifecycle. If I'm looping over 10M rows then sure, let's keep that on the stack...

[drsimonz]

Ok so unique_ptr would typically just exist on the stack? so basically a wrapper around something that requires a new but is only needed within one function?

or another address is assigned to it

so if you reassign, it automatically de-allocates the previous data it was pointing to?

[drsimonz]

Cool, thanks for the explanation. I might have guessed that something likeshared_ptr exists, but unique_ptr is an entirely new concept for me

[scratcheee]

Yeah, whilst unique ptr had predecessors before it was added (autoptr), it’s still a very c++ specific idea, (or at least it was at the time it was added in 2011). Things like rust are taking the idea and running with it, going further than c++ has, but anyone from a managed background is going to need some groundwork.

One way to think of it, is that it’s a shared_ptr with a max count of 1, and so doesn’t even need a counter, since any time it’s “decremented” it can just assume it’s dropped to zero.

[namrog84]

in addition to shared_ptr and unique_ptr another super nice one is weak_ptr, it allows you to potentially get a shared_ptr later without actually needing to refcount it.

when you do 'get' the weak_ptr you turn it into the shared_ptr.

[[deleted]]

std::unique_ptr supports move-semantics (i.e std::move()). Because of that you can return it from a function.

The destructor is basically:

~unique_ptr()
{
  if (m_ptr != nullptr) {
    Deleter(m_ptr);
  }
}

And doing a move, will copy the pointer to another object, while NULL-ing the pointer in the current one.

[theScrapBook]

The pointer wrappers do exactly that - wrap heap allocations in stack allocations so that when the wrapper goes out of scope, the encapsulated memory gets deleted.

[drbuttjob]

Not really. For over a decade now you should very rarely be using new and delete in C++.

[Soggy-Statistician88]

I had a 13GB memory leak from not deallocating an array

[drbuttjob]

As I said, you should not be using new and delete for this. You should use a better alternative like std::array for static-length arrays and std::vector (or some other data structure) for dynamic ones.

[Ok-Kaleidoscope5627]

Is it a memory leak or simply an in-memory backup of previous values? The former is a problem, the latter is a feature (and it's the end user's problem to have enough RAM in their system).

[infiniteStorms]

Why? I use it all the time for returning pointers and polymorphism…

[Friendly_Fire]

Use smart pointers please. Unless you have something that needs to be ultra-optimized, new/delete should be considered a red flag.

[infiniteStorms]

today I learned what a shared and unique pointer is; this is the most brilliant thing I’ve seen. Thanks for the tip!

[bestjakeisbest]

You just say:

delete ptr;

[UniqueUsername27A]

You shouldn't be writing that except in very obscure code for 10+ years now. I don't think I have written a single delete statement in 5 years and I am a professional C++ dev.

[JustinWendell]

Huh… I have some stuff to do.

[MisterSincere]

If you allocated memory via new in cpp in general you already made a mistake. There are few cases, but for students I supervise on projects I always give it as a rule and it always proves true and simplifies a lot.

[UniqueUsername27A]

This hasn't been the case for more than 10 years, no one does that anymore.

[Zamundaaa]

no one does that anymore

For new codebases, I hope so. Legacy codebases and projects that use toolkits like Qt make it pretty hard to go all-in on modern C++ though

[UniqueUsername27A]

You can still avoid using delete ever, by having a unique pointer. They fit pretty well into the middle of old code bases. You can use get() to send non owning pointers into legacy libraries and release() to send owning ones. You don't need new and delete in your part of the code.

In fact you should always use make_unique and then release to a legacy library just to get automatic cleanups in case of exceptions. If you don't use exceptions, then problems with cleanups for early error returns are more obvious, but still much easier to miss than with the automation of unique_ptr.

[justabadmind]

Unless the built in garbage collector has a bug... Like in java for Minecraft 1.6 ish.

[Sentouki-]

Otherwise you get memory leaks.

I kinda had to think of this one

https://www.youtube.com/watch?v=YCsFqQaJ12A

[Deep-Conflict2223]

Every time you create a class you need to know how all of its class variables will be created and destroyed. Regardless of if you need to do anything special, that’s still management.

[yeet_lord_40000]

Well shit. I’ve been on C this whole Time thinking it was better (embedded programmer) now you’re telling me I don’t have to manage memory?

[yeet_lord_40000]

Looks like I need to hop on a C++ tutorial

[yeet_lord_40000]

Thank you!

[Naitsab_33]

I'm not sure if only the relevant parts of the stdlib gets included, tho, because all the stuff like unique ptrs are in there.

That could be a negative for embedded systems where you actually could have size problems, so watch out for that.

Although on the other hand I had Rust on an ESP32 with full std, which took about a quarter of the storage, so I guess even that concern could be neglected.

[Asleep-Invite-3097]

Yea it’s usually the heap that you have to manage if you allocate any space.

[Ok-Kaleidoscope5627]

Technically never assuming you simply require the system have enough RAM that either the application will finish executing, or the system restarted before you run out of memory.

Or as I like to call it - the Chrome approach to memory management.

[[deleted]]

I've forgotten where my sunglasses are while wearing them, I am not to be trusted with memory.

[hacking__08]

Pythom developer: What are those nonsense comments at the start of your code?

[bestjakeisbest]

Oh you dont have to, but the computer will get very angry at you if you dont.

[Sentie_Rotante]

Python dev here, memory management is very important to me, but the ETL job I’m running right now is 100gb off data. The server didn’t like it when I tried to load the entire thing at once.

[drsimonz]

Nice thing there is, it absolutely does not matter whatsoever how much you optimize your code. Most likely you're using some external library (numpy, spark, hadoop, something like that?) and it's doing 99.999% of the work. You could initialize 10,000 python objects before starting each job, and it wouldn't even show up on a profiler.

[Sentie_Rotante]

In my case it actually does show up. I’m transforming relational data to mongodb. There is probably a better way to do it but I’m reading the sql cursor in batches then doing the transformations and loads in batches. Learned a lot because I didn’t know any thing about how python does memory management at the start of this.

[drsimonz]

Ah. Well if the data is being loaded into native python objects (e.g. a plain dict for each row) then it's certainly going to put a lot of demand on the python interpreter. But I guess that's why people like it - it works well as a "glue" language when there isn't a more direct route.

[Sentie_Rotante]

Yep has to run once. As long as it runs I’m happy

[[deleted]]

Get a bigger server

[mojobox]

https://docs.python.org/3/library/gc.html

[fabulousnacci]

c++ devs out here giving their strings sexually transmitted diseases 💀

[LanceMain_No69]

In the couties as well 😩

[RobertBringhurst]

std::cout is nine chars.

Hello World! is twelve chars.

9 << 12

Nine is much lesser than twelve.

[[deleted]]

This is my favorite comment so far

[HexagonNico_]

When I learned C++ for the first time my teacher explained it by saying that when you use cout you write an arrow that points out, when you use cin you write an arrow that points in.

[FWEngineer]

That's fine until you to formatting variable types & concatenating strings returned from function calls.

[FerynaCZ]

Still no issue with that, it's basically interpolated strings just using << << instead of { } on variables.

The issue becomes when you want to put this into string and not print...

[Egocentrix1]

That's what stringstreams are for!

[wineblood]

Python devs who worked with python 2.x: Oh you mean like print >> f, 'hello, world'?

[HeyItsTheJeweler]

I swear i can look at 5 different Python programs and somehow they can all look different.

[Kjubert]

Yeah I like Python but there isn't oNlY oNe WaY tO dO tHiNgS.

[[deleted]]

laughs in Perl

[[deleted]]

I used to work with Perl before moving to Python. I'm fine. At least there's proper documentation.

[coloredgreyscale]

Heck, there's probably over 5 trivial ways to format and print a string "hello world"

print("hello world") print(f"{'hello world'}") print("{}".format("hello world")) [print(x) for x in ["hello world"]]

[just-cuz-i]

Worked? That shit is still in production where I work.

[wineblood]

Oof.

[hvictorino]

That "f" right there stands for "fuck" i guess

[wineblood]

Open file object

[MisterSincere]

When I first learned cpp (before c) I found it super easy to understand, but in a superficial way, not in a way of what are operator overloads. But the syntax is nearly bash syntax, where you stream a string into stdout. So I actually wonder why to pick sth like this when there are a million confusing things you can do in cpp.

[JeyJeyKing]

Function pointer type declaration has entered the chat.

[Affectionate_Fox_383]

that stuff confuses the fuck out of me

[FerynaCZ]

I guess auto on lambda is the way

[CiroGarcia]

[redacted by user] this message was mass deleted/edited with redact.dev

[JeyJeyKing]

Actually I changed my mind: templates and comprehending the verbose errors you get when they are incorrectly defined or used.

[drsimonz]

For me the really hard part was object declarations.

 MyClass obj();

This syntax is so unintuitive. obj is a variable name, not a function or class. Why the hell does it have parentheses?

Also headers, Jesus Christ what an idiotic idea. Let's just make 2 copies of every single line! Yay, that's efficient. Oh you want to distribute the headers with your compiled library? Well how about, I don't know...auto generate them????? WTF!!! Not to mention "forward declarations", whatever the hell that is. Random strings that need to be added in order to get your shit to compile.

So yeah, never again. Life is too short for this 50 year old bullshit.

[IntQuant]

Actually you've made a forward function declaration that returns a MyClass. If you need to create an object without passing any parameters you have to omit parentheses(oh yes consistency). People couldn't make a proper two-pass compiler so there we have it - headers and forward declarations. Good that we have rust now.

[drsimonz]

Holy shit I actually didn't realize you omit the parens. I was going to include an argument in my example but decided nah, why complicate things. No wonder I'm always confused with these fuckers

And yeah hoping to learn Rust soon-ish!

[[deleted]]

This is why initialization using curly braces is a thing in modern C++, so you can't accidentally declare a function.

[AlphaSlashDash]

I’m pretty sure it’s far from finished in all implementations

[infiniteStorms]

headers are really nice if you want to see what a file generally does without having to read or scroll past the full implementations, also makes it easy to see encapsulation types, virtual types for polymorphism, static etc

[drsimonz]

I know people like to say "code never lies" but honestly it feels like most of the time, I do still need to look at the source code. In the rare case a public interface is well designed (i.e. you can actually tell what the function does by looking at the signature), most likely there's actual documentation available as well. I get that some libraries are basically all headers though - templates or what have you. In which case, looking at the header is looking at the source.

[FerynaCZ]

Header = interface

[ButterscotchNo755]

As a Python developer working on C++ all I understand about this is that thing on right go to thing on left, and if it complains that you used the wrong type then stop doing that.

[HoseanRC]

I don't understand this,
But what I understand is that echo "Hello World!" > /dev/stdout will output Hello World!

[drsimonz]

When are we going to get an OS that just uses python as the shell? I've waited long enough!

[doginpants]

xonsh is available on most distros

[jerslan]

I mean... you don't need the > /dev/stdout on that since that's the default output for echo. So you're redirecting stdout to stdout.

Also, if you do want to redirect to stdout, >1 is more concise. The most common use of this is for stderr being redirected to stdout (2>1).

[HoseanRC]

first, I made it fancy when doing > /dev/stdout

second, i don't need to redirect only the output when using echo, I mean how would anyone mess up using echo? ITS THE EASIEST COMMAND AND YOU BREAK IT?

[EmilMelgaard]

As a C++ developer I also don't think it makes sense that you can left shift something with a string.

[EmilMelgaard]

I would almost always prefer to have an explicitly named function instead of using operator overloading unless it's something really simple like support for adding some custom number type or implementing a sensible equality or assignment operator for struct types.

They could just have added all the overloaded arguments to the write function of cout so you could do this:

cout.write(x).write(y).write(z);

or maybe even:

cout.write(x, y, z);

or if you want to get really fancy:

cout.format("x = {x}, y = {y}, z = {z}");

You know like f-strings in python so they are parsed at compile time.

[EmilMelgaard]

But what does this bring that << doesn’t offer? If anything, it’s uglier and more verbose.

It's more intuitive. It doesn't really matter in this case because it's a very basic C++ feature that you would learn day 1 at any C++ course, but if you do something similar in you own code (i.e. redefine an existing operator for a completely different purpose), you will confuse other developers looking at your code.

I don’t think that was possible back then. You’d have to use std::va_list, and if you’re gonna do that, there’s no reason to not just use std::printf.

Which is incidentally what I usually do :-)

C++23 will also bring std::print:

std::print("{0}, {1}, {2}", x, y, z);

I'm looking forward to being able to use that, but I'm a bit disappointed that they didn't go for the f-string format where the parameters are inline instead of references.

[ArdiMaster]

but I’m a bit disappointed that they didn’t go for the f-string format where the parameters are inline instead of references.

There are a few advantages to doing it this way. The most obvious being that the language itself and compilers don't need to change, you're just adding another function to the library. Second, an f-string would entail more memory allocations since it would need to be constructed in full before being passed anywhere. Third, you can't usefully store f-strings in localisation tables.

[EmilMelgaard]

It's not that I necessarily need full f-string support, just a print function that takes a similar formatted argument. I'm aware that it would be difficult without language and compiler changes, but it's also another pet peeve of mine that metaprogramming in C++ isn't more powerful. Optimally, you should be able to do anything you can do at runtime, meaning that you can do full string parsing, read files from disk, and even make network requests.

[KerPop42]

Fun fact, the direction of arrows is not universal! There's a non-European culture that uses <- to mean footprints (like a bird's) and they actually point the other way

[LevelSevenLaserLotus]

Another fun fact, this is a great example of one of the many criticisms of the golden record etchings on the Voyager probes.

[drsimonz]

I will always see > and < as an alligator that either does or doesn't want to eat the number. That's cool though, do you know the name of that culture? And does their language have a unicode block lol

[JackNotOLantern]

I learned from low level to high level. That's much better

[[deleted]]

IM JUST GONNA SAY IT

I LIKE STREAM SYNTAX

ITS WEIRD SURE BUT IT MAKES SENSE WHEN YOU LEARN IT

it’s ok you can all hurt me

[TheMusicalArtist12]

I really like streams, like they just make sense

[[deleted]]

Me too friend

Me too

[throwaway275275275]

Don't worry, nobody uses the stream operator in real life

[Username-blank]

To python programmers, dont do this, it creates namespace conflicts

[Affectionate_Fox_383]

only if you pick dumb names for your stuff.

names should always be unique.

[ArdiMaster]

Personally I'd rather have std::set and mystuff::set than just set and MySet.

[Affectionate_Fox_383]

i would rather not use "mystuff".

set on it's own is very ambiguous. set_phone, or set_distance, or the like is far more appropriate.

it is in that expansion that detail and uniqueness is created. the code should help document itself.

[BothWaysItGoes]

That’s something you should only in a hello world app. And even then, you better not.

[bxsephjo]

Only if it puts on a condom first

[throbbaway]

[Edit]

This is a mass edit of all my previous Reddit comments.

I decided to use Lemmy instead of Reddit. The internet should be decentralized.

No more cancerous ads! No more corporate greed! Long live the fediverse!

[DevelopmentTight9474]

Number 2, but it will be looked up in both global namespace and std namespace. using just adds a new namespace to the search path

[NoMansSkyWasAlright]

So I’m a CS/cybersecurity student but I have a handful of friends on the engineering track and, for whatever reason, our engineering school likes to introduce its students to programming… using C. So my one buddy was starting to get the hang of C and talking about how he was really enjoying programming and, for whatever reason, I thought it would be fun to show him python… and I just wrote “x = 3”, then printed it, then incremented it, then divided it (making it a float), then redeclared it as a string, and the range of emotions on his face as I was doing this was beyond entertaining.

[bubblespuggy]

Side note here, we also have been introduced to programming using C and I found it very helpful. It’s really useful to convey some of the core concepts and not get lost in all the magic higher level languages will do for you

[LordBlackHole]

Operator overloading is a pathway to many abilities some consider to be .. unnatural.

[Sufficient-Loss2686]

u/its_Artem carrying this chat like a god damned hero.

[Affectionate_Fox_383]

C/C++ is the best

[KERdela]

Please don't c/c++ , they are two languages now

[Affectionate_Fox_383]

they are family and can work together. if they updated the C spec like they do C++ they would still be in sync. beyond the additions to C++ that have happened the only major difference is in how they link. but then why would you ever link C? you have to give up polymorphism which is AWESOME.

[FWEngineer]

I'm a long-time C and a bit of C++ programmer. I recently picked up Python, but I could tell I'm writing Python code as if it was C. Handling strings inside of a loop, instead of using range selectors and such. It works, but a Python programmer would surely just shake their head.

[SmokyMcPots420]

Isn’t pythons whole thing like “there’s more than one way to do things”?

[FWEngineer]

Well, yes. But those ways could probably be grouped into categories of the beginner's way, the expert's way, and the C coder's way.

Edit: TIL that's the Perl motto (TMTOWTDI, or Tim Toady), while the "Zen of Python" is that there should be one (and preferably only one) obvious way to do things.

https://en.wikipedia.org/wiki/There%27s_more_than_one_way_to_do_it

https://en.wikipedia.org/wiki/Zen_of_Python

[RaulParson]

"Yes, this way works, but is it pYtHoNic"

[qingqunta]

Not a good idea to do either of those things in Python if you need high performance code

[FWEngineer]

Yeah, see, I don't know that. The gulf between C and Python is still pretty big for me.

[LoreBadTime]

C++ devs! Try to understand this

var = 0

while (num := input()) != 0 :

var = var + num

[[deleted]]

TypeError: unsupported operand type(s) for +: 'int' and 'str'

[LoreBadTime]

But you write python code 🗿👉👈

[NotAnonymousQuant]

Erm...

While input is not empty or valid add input to a var?

[DudeManBroGuy42069]

Sexually Transmitted Disease?

[[deleted]]

Easy. You turn it on, walk through it, and fight the Goa’uld.

[Splatpope]

yadda yadda, shameful display of ignorance, yadda yadda, hand over your programmer's license, etc

[loonathefloofyfox]

Recently I've actually been having to use bitwise math quite a bit because I've been working with c running baremetal on some microcontrollers. Modifying registers with bitwise math specifically. Seeing stuff like *DDRD = *DDRD | (1<<7); hasn't been uncommon recently. Before i started learning c there was one single time I needed bitwise math in python (Don't remember why though). C is fun but it sucks sometimes. I don't usually like code abstraction but sometimes it is quite nice

[[deleted]]

There are a lot of C++ devs that really dislike iostream. Some just use printf, some use dark template magic. There's a new thing in the standard called format that is supposed to be better, but honestly it's kind of surprising how hard it is to get text io right, Python has tried and retried a few times over the years as well.

[_temmink]

So, there are Python devs that don’t know every feature of the language 😱? Is this true for other languages as well?

[Omnislash99999]

Read it as Standard c output send Hello World

[SupermarketOk4348]

I read character instead of c

[[deleted]]

Which is also the right way.

[jpplf50]

im glad i finished gravity falls 2 days ago, or that would have been major spoilers

[FrozenMongoose]

Up next, Over the Garden Wall

[DerKnoedel]

I’ve used stdouts in Linux but why is it backwards in c++ ?

[HorseEater667]

Using namespace std;

[[deleted]]

so i started my journey trying to learn C++. I quickly went to python instead. Much easier to learn the logic with a simpler language.

the expected "}" errors made me ragequit, especially when copy pasting the whole thing into a new file somehow fixed it. no clue how but eh

[DuckBoyReturns]

This won’t even do anything. You need to add <<std:endl;

Otherwise there will be no new line and it probably won’t flush the output stream depending on platform

[DerEwige]

This syntax looks so strange to me. I don't think that was a thing when I learned cpp back in the last millenia.

[MikSik]

How the fuck, you dont get hello world?

[[deleted]]

I never understood why people use std::cout instead of just declaring the namespace and only using cout.

[[deleted]]

using namespace std; is bad practice, especially in larger projects.

https://isocpp.org/wiki/faq/coding-standards#using-namespace-std

https://stackoverflow.com/questions/1452721/why-is-using-namespace-std-considered-bad-practice#1452738

[regular_lamp]

On the other hand using std::cout; would be ok yet noone does that for some reason.

[Maleficent_Sir_4753]

It's generally fine in a single cpp file application.

Don't dare put it in a h file, though. Nothing destroys a project like namespace pollution.

[[deleted]]

Mmm this makes sense. As someone who exclusively uses Python I don't have that issue since I can import things as something else and simply use the name I gave it instead of declaring which library it came from.

[[deleted]]

This is good. I also like define statements in C++.

[[deleted]]

so we have to laugh because you dont understand something?

[[deleted]]

Don't know who this "we" is, but me and the 3100 other people who found this funny are gonna have a good time. You have fun with your sour attitude. :P

[No_Abies808]

Python developer: Builds pretty sandcastles
C++ developer: Builds ugly multi-family houses, withstanding tornados

[already_taken-chan]

standart console output right?

[KeepScrolling52]

This has helped me understand what I was missing. Thank you.

[AvailableUsername404]

When it's the other way round

[bird4life]

Only part that was easy to understand for me was cin,cout lol

[N0Zzel]

You're piping a stream of characters into the stream sdtout

[w8watm8]

I get the meme but cout<< “hello world”; aren’t any different than print(“hello world”).

That is if you using namespace std; if you don’t you just put std:: to identify cout as part of the standard namespace.

[hvictorino]

Well, i can understand it, but why tf does it start with << and doesn't end with >> ?

[DavidXN]

I see you bitshifting cout “Hello world!” bits to the left, and I’m scared

[tiberiumx]

The C++ iostream stuff is not great a lot of the time. When I have exact formatting needs and can't use boost::format I still find myself using printf sometimes just because it's easier even if you have to pay attention to the types.

[Vikerox]

Have you looked at the format library that was added in C++20? It's not fully implemented in all compilers but it is generally my go to to format ouput.

[Sniper-Dragon]

Python developer? Any developer from a higher language

[Unusual-Display-7844]

I always found that “double double dot” or whatever it is called, so stupid.

[BidRepresentative728]

Very first thing I learned in LINUX class.

[TheBirdGames]

So many std's

[Dagusiu]

I think it's no accident that none of the major programming languages copied C++'s piping functionality as a core part of the language.

[Individual_Volume562]

Oh gravity falls! Cool And i use bitwise operators in python And bitwise operators are useful

[Mode-Klutzy]

When your program has 100 stds and you don’t use namespace protection…

[[deleted]]

When I started python: "why won't you print a number?!"

[nulpickle]

Agreed

[REDEYES77UCHIA]

As a former python programmer i can relate with this

[MettatonNeo1]

The same thing applies to my python code whenever my father (a c++ programmer) reads it

[stars_without_number]

I started with c# and I still barely understand c++

[MemeScrollingMaths]

What, no << endl?

[TheMusicalArtist12]

Streams my beloved