This Is Why Python Data Classes Are Awesome

[@ArjanCodes]

💡 Get the FREE 7-step guide to help you consistently design great software: arjancodes.com/designguide.

[@hematogen50g]

I came to Python from C# so I picked up coding quickly. But thinking in python way is harder, so such videos really help me develop python mindset.

[@Volcan-kf3oz]

This guy really know what he is doing every video I've seen he able to break it down to where even a person new to python can understand "if you can't explain it simply, you don't understand it well enough." - Albert Einstein

[@ArjanCodes]

Thank you so much!

[@coupmd]

Enjoyed this video. Would enjoy more videos on intermediate/advanced python standard library tools and their examples of their intended use cases.

[@paulorsbrito]

What happened to “explicit is better than implicit” and to “there should be only one obvious way to do something”?

[@beershigachi4797]

Zen of Python. I love that. So when I saw dataclasses I decided to use Haskell as my primary language.

[@sbeau]

Arjan, your ability to explain detail in a structured, easy to follow format is second to none. Thank you for another great tutorial.

[@VladimirSanchez]

He's in the same league as Nana! ;)

[@Cookie-mv2hg]

Since we're talking a lot about dataclasses, I wonder would it be great combining with sql database. If we could get a review that would be very helpful!

[@ritzg98]

This guy is excellent. I've only watched a couple of his videos so far. Planning on watching a few more today. Clear, concise, accessible. So far, great!

[@ArjanCodes]

Glad you like them!

[@bryan_hiebert]

Just like every video from you my knowledge of programming with python is advanced. I really appreciate the content you provide, thank you!

[@equu497]

I wasn't even trying to learn about dataclasses...but it came up on my recommended and I watched the entire thing- Got me thinking I should clean up some old code.

[@mpotane]

Wow, the most complete tutorial I've seen. Not a single detail has been missed.

[@ArjanCodes]

Thanks, glad you liked it!

[@Rebeljah]

I am 100% gonna use the repr=False option, thank you!

[@cheesecake_mafia]

I think you might find this interesting if you don't already know, but you can define class variables while using @dataclass. You just need to import ClassVar from typing and then when you are defining the class variables, use ClassVar after the colon and then put square brackets and the datatype of the class variable. I think this feature was mentioned in the documentation and also Tech with Tim channel helped me realise this. Great Video! Cheers.

[@ArjanCodes]

Interesting, didn’t know that was possible. Thanks for sharing!

[@Rebeljah]

New AC video! I am actually using DCs right now to define a common set of data for server/client communication. It's very nice because I can subclass a super dataclass in order to get functionality like serialization/deserialization fairly easily. Adding new data types just takes a few lines of code now!

[@centar1595]

So you're enjoying the AC/DC video? :)

[@Rebeljah]

@@centar1595 yes I am! Lol

[@SiarheiAkhramenia]

My God, what an incredible sound quality!

[@ArjanCodes]

Thanks!

[@sambeard4428]

Geweldig en duidelijk overzicht van deze erg handige feature. Gisteren liep ik precies nog tegen deze use case aan, veel boillerplate code. Dit lost het mooi op. Thanks!

[@wtfKwaku]

OMG, I been working on this project and for like 3 days I been trying assign a class and return something! Great Video!

[@ArjanCodes]

Glad it was helpful!

[@FrankenLab]

@ArjanCodes, great video. I consider myself a casual programmer and have been programming with Python for about 5yrs and absolutely love it. I started programming "casually" in the 80's with C, Pascal, Assembler, then Perl and now Python. I really enjoyed C and Perl, but Python is by far my favorite now. This is the first video I've seen of yours and based on that I just subscribed to your channel. I enjoy your style and explanations and I don't have to play the video at twice the speed waiting for you to get to the point. I'm looking forward to seeing more of your Python videos.

[@davidlakomski3919]

I've tried 2 days ago to make a package to manage state of jobs with Pydantic, and even if it was less messy than what I did before, I realize now how easier and cleaner it would have been with dataclasses ! Thanks for the excellent content !

[@ArjanCodes]

Glad it was helpful, David!

[@mampiisaotaku]

i just discovered your channel a few videos back. and what you share is pure gold

[@ArjanCodes]

Thank you so much, glad you like it!

[@mauisam1]

Again Arjan, another fantastic video. If I become half the programmer you are I will be lucky. But I just have the love of programming so I will continue to work on improving my knowledge and skill set. So many programmer say just read the Docs, but I learn from examples and the Docs usually have few if not poor examples. So a big part of my improvement will be in thanks to your love of sharing your knowledge. Thank you...

[@alfonsov3190]

I had a couple of questions during the video, but immediately after they surged, you addressed them. Thanks a lot, as usual!

[@ArjanCodes]

You're welcome :).

[@marcioneto3016]

Amazing video, as usual. Here's a suggestion: how about a video on the infamous Visitor pattern next? Thanks for the amazing content. I really liked the Software Designer Mindset course, by the way.

[@ArjanCodes]

Thanks for the suggestion, Márcio, and glad to hear you enjoyed the course!

[@nicolasRebagliati]

if you use init=False, the repr=False should be implicit. Because if not the repr generated is invalid, because repr should generate an object equal to the original if you copy and paste it. Also you forgot to mention that if you use slots you cant not add attributes in runtime to your object

[@DrSpooglemon]

This does seem like a massive bug. I wonder if it has been/will be cleaned up by the Python maintainers.

[@jma42]

I also want to add that you can actually use asdict method from dataclasses and from_dict method from dacite library. It works as it sounds to be and even works in nested dicts/dataclasses!

[@nedegt1877]

I think it's better to have more in depths Python video's like this one instead of trying to limit your options. I mean if you search for Python you will find 1000's of "Hello World" Tutorials, some "How To's" but little technical explanation of the language it self like your video. I believe that if you can learn to master the language you can also master the challenges a language gives you. But since most Python programmers are "Self taught programmers" their knowledge is mostly limited to the sources they managed to learn from. Knowing the functions or having a list of the language API it self is not enough. Some examples of use cases like your video are very welcome. Thanks!

[@WalterBoring]

Cool video. I didn't even know about the dataclasses lib until this. I'm putting it into my project now.

[@amosmunezero9958]

Great tutorial in Python, its been a while I havent done some Python, I didnt know much about DataClass. So thank you.

[@zuydra]

Hi Arjan, your videos on Python are the best I have ever seen on KZbin. Please keep up the good work 👍

[@ArjanCodes]

Thanks so much! And will do 😊

[@christensencode7538]

Your videos on dataclasses are awesome! I've used them for a few projects and they really help.

[@barrykruyssen]

Hi Arjan. Great video, very well presented. I've just found your channel and will be watching all your videos as time permits. I'm a retired software engineer (started back in the early 80's). 5 weeks ago I decided, in my retirement, to switch back to linux (and python - which I have never used), just for fun, after 25 years in microsoft products (prior to that I was in the Unix world). I'll be changing 2 of my classes to data classes ASAP. I have just read your Software Design Guide and agree with much of what you've written. I think you have glossed over the most important aspect "Who’s it intended for?". Determining who is doing what, why they do it and what they expect from it and then managing the expectations is the key to a successful implementation. You do mention your “zoom out and zoom in” approach which probably encompasses this but in my planning, the people are the key and if there are problems in this area it can be very costly down the track (we qualified our prospective clients and if the people problem was too great we walked away from deals), as you say we write the code for the client, not for us. Thanks

[@flynnowen2478]

Love your content Arjan! I've been making an effort to apply your teachings as much as possible in my code. Would you consider doing any future videos on unit testing? I think it would be super useful. I personally use pytest, but you might know better frameworks.

[@XCanG]

I use similar thing when working with fastapi, library named SQLModel, what it basicaly is very similar to dataclass, but it has validation from pydantic, so if you, say assign to person with a name type int, like Person(name=1), then you get ValidationError exception. It is more useful in fastapi as it may be used as a mechanism to prevent API being called and executed if provided arguments are not match. And you can have more validation methods in Field, like: le, ge, lt, gt; for list types you may provide min/max range, for strings you may add regex or even something more custom via function. I like it a bit more than just dataclass

[@amadzarak7746]

Wow! How did I JUST find this channel. You are awesome man!

[@ArjanCodes]

Welcome aboard! :)

[@ninadloke785]

Watching your video for first time. Deserves subscribe!! Great work and thanks!!

[@wv1138]

Good point about a possible strict mode

[@justinpeter5752]

Very good video. I think I learned a lot about classes in this video and I can see where I can use some of these in my code. Well I’m not quite there yet with building classes with multiple inheritance to worry about the issue with slots. But at least I’ll start using slots for performance improvements. Overall, bravo. I’m starting to understand more about Python from a systematical perspective.

[@ChrisPatti]

I really love this video! It’s an excellent quick, guided tours to how powerful data classes, can be. Thanks for making it!

[@ArjanCodes]

Thank you Christopher. Glad it was helpful!

[@qrubmeeaz]

... aaand he's done it again!! Brilliant! Thank you.

[@hisamsowaib956]

Hope you can create a video on how we can use dataclasses with data coming from db. I think that is a more real life scenario. Thanks a lot.

[@Ziggity]

Excellent video, but ever since your video about Pydantic I just don't use dataclasses anymore. Would love to see a follow up for Pydantic as well =]

[@pallu83]

me too, Pydantic is even more amazing and works in older Python versions too.

[@Kirac322]

Great video Arjan! Learned quite some new things even though I regularly use dataclasses. One suggestion which I encounter quite often in data science: Where and when to properly calculate additional properties (features for my models) after first initialization when there are dependencies between multiple objects, e.g, you have to wait for both to finish initialization, then calculate features. I'm currently working with a hirarchy of dataclasses and calculate these properties in the top level in __post_init__ but am unsure if that's the best way. Thanks!

[@ArjanCodes]

Thanks so much, glad it was helpful!

[@rrestituti]

Amazing video. I didn't know dataclasses and I found it amazing. Thanks, Arjan . Got a new subscriber.

[@ArjanCodes]

We're glad to have you, welcome aboard!

[@christopheanfry2425]

Thank you so much for this video and for the design guide I’ve just download, it’s literally gold 🙏

[@ArjanCodes]

You’re welcome! Glad you find it helpful.

[@danieleatzeni2437]

Hey man, cool video! I saw that when you set frozen=True, you got an error in the __post_init__ (not in the main). Is there a way to use __post_init__ for frozen dataclasses?

[@funkenjoyer]

I ran into this issue some time ago, apparently u can't do it directly since that would require you to change the object which is prohibited by the frozen=True statement (according to documentation __setattr__ and __delattr__ methods are added which will throw the error). But u can get around that using object.__setattr__(self, 'field_name', field_value) which is whats happening in the __init__ anyways (i guess it circumvents the __setattr__ method defined in class and calls the definition directly from the object class)

[@LeteFox]

you can use super().__setattr__("_search_string", f"{self.name} {self.address}")

[@funkenjoyer]

@@LeteFox yes as long as the super class isn't frozen itself, altho if you're not inheriting from anything it's more concise

[@kunedroid3446]

I was just on this issue too... I don't know mate, it seems that python is trying too hard to add features which it was not well planned to and we are ending up with so many esoteric rules/details that learning python by anything other than reading books on "how to adhere to the pre-defined rules/standards of keywords" will soon be impossible..

[@ArjanCodes]

I would actually use a different approach altogether if you want a frozen dataclass, but still would like to have a search string like in the example in the video (didn't have time to cover this because the video was already quite long). I wouldn't store the search string in an instance variable, but use a property instead. It would mean that you need to compute the search string on the fly every time though, so it might not be the preferred solution if you need to access it often, but I think it is a lot cleaner than circumventing attribute assignment using __setattr__.

[@shpresimmuja467]

Python went full circle, brought types back

[@MichaelMorenoPhilosophy]

I think 5:15 is wrong as those are not class variables, they're member annotations as per PEP 526. Initializing them on the same line would make it them class variables though.

[@nusermane1076]

Incredibly good explanation, will try this for myself tomorrow 👍👍👍

[@SystemSigma_]

Nice overview of dataclasses.. Next, we need an extensive video about the testing frameworks and mocking for TDD!

[@DonRenny83]

Mark Sheppard teaching python...now that's supernatural! Thanks for the video!

[@marknielsen4494]

Super high quality content - thank you Arjan!!!

[@ArjanCodes]

Glad you enjoyed it, Mark!

[@robboerman9378]

I love your concise and clear explanations. Going to look into your course!

[@fuadpalchayev7269]

Thank you Arjan!👍

[@agnichatian]

Scrutinizing your error code printout @13:29, It seems like a design flaw to not allow even __post_init__() to change the fields.

[@anton-r]

wow, 9:33 looks like python has private values now, nice. tnx a lot

[@aungkyawkyaw9114]

next level! Thanks Uncle Arjan.

[@AutoFirePad]

No behavior...amazing anti-oop style.

[@NeumsFor9]

Do you do a video on the impact of slots on bulk data engineering?

[@fvbakel]

Great overview of the dataclass. I wonder what your view is on binding the dataclass to a SQL database. Is there an easy way? It seems that the Django and sqlalchemy methods are not compatible with the dataclass? Further more, what do you think about nested dataclass and the impact on hashing?

[@anonymous102592]

Thanks , great explanation, and overview

[@ArjanCodes]

Thank you for the kind comment!

[@emory_blame]

Hey. Nice video) Everything were fine and helpful until the 21:00 where you suggest to not using the inherent. For newcomers to python I can suggest video called super - is super. It were very helpful to me.

[@8bitscoding220]

Cool video, thanks for it. I think that I would argue that if there are valid arguments against multiple inheritance (and valid arguments in favor of it), the limitations of an oriented object language should not be considered one. To make Python better we have to stop defending the poor design choices that were made in the past and move forward (I'm all in favor of breaking things if I can finally write def myfunc(myarg=[]) like in any other language, for example).

[@umarhussain9334]

I usually use set attr for post init which I assume was wrong. Thanks Arjan

[@rablaze]

Love the videos! I was watching a rerun of a Supernatural episode while watching this and the actor that plays Crowley and you kinda like alike lol

[@ArjanCodes]

LOL, I see what you mean :).

[@seans9168]

Great overview and useful examples! Thanks for the video.

[@AlanHernandez-mw6xb]

This was actually very entertaining. Thanks!🎃

[@ArjanCodes]

Thanks so much Alan, glad you liked it!

[@hcubill]

Love the video Arjan. It's great you explain the new features in 3.10. in my team we wonder what the benefit of upgrading is and this helps a lot!

[@alejandropereira5680]

Very useful explanation, to the point and with real use case, really liking these vids

[@ArjanCodes]

Thanks so much Alejandro, glad you liked it!

[@zakseipel9494]

Talking about strict mode that was one of the reasons I started using Black and setting it to a very strict set of rules. It forces me to write leaner code and not be lazy. Comes at a price of extra dev time but worth it.

[@presstv]

great video. Thanks Arjan

[@kevindtimm]

your frozen=True has an unpleasant side effect, you also can't run your __post_init__ function because the class has already been created and is immutable (so says your output and mine too)

[@AndreyPutilov]

Great explanations! Thanks for the content!

[@andreasthegreat8509]

I’ve done functional and OOP, I prefer functional all the way. Racket has some great magic

[@andrewmartinez8340]

I'm trying to wrap my head around a use for this because most apps will use a orm

[@JPy90]

Awesome man.! Just arrive to your channel. Seems amazing

[@DataScienceGarage]

Very useful. Thanks!

[@ArjanCodes]

You’re welcome!

[@ShahriyarRzayev]

Awesome material as usual, keep going and thanks for sharing)

[@MH-oc4de]

That was interesting, thanks! FYI: the performance improvement for me (on mac os) dropped from about 20-24% under python 3.10, to only 2-2.5% under python 3.11.

[@solvability2782]

very cool. I will check it out.

[@abdelkadergnichi6643]

You are awesome man i really appreciate you work bro your videos are so clear and beefy ❤❤

[@ArjanCodes]

Thank you so much! ❤

[@metensis]

Great video! You may want to add in a new video the new feature of 3.10 to allow children dataclasses with kw_only

[@dabunnisher29]

Didn't know about these. Thank you SOOO MUCH!!!!

[@ArjanCodes]

I'm glad the video was helpful!

[@ErikS-]

Great to see that the dutch "orange army" is also great at making python lectures👍

[@ArjanCodes]

Thanks Erik, happy you’re enjoying the content!

[@douglaspiresmartins2955]

Hey Arjan, excellent content. You mentioned Data-Oriented, do you think dataclasses can help too much with that? Help to split "data entities" and "code modules". Perhaps you could do a video about that. Many thanks!

[@ArjanCodes]

Thank you, and for sure that's possible! I like to use dataclasses for representing structured data, maybe add a few methods that operate on the data (but keep it limited), and then organize the rest of the code in functions and modules, and decouple them with abstractions (abcs or protocol classes).

[@xl0xl0xl0]

Thank you for the video. You could use the Jupyter integration with vscode to avoid switching back and for the between code and output.

[@ArjanCodes]

Thanks for the suggestion - will look into this!

[@richardmonteiro8694]

so slots =True is just when retreiving infor for computational pov?, and an amazing video once again!

[@georgikostov6982]

"Stop it ...Get some help" :) Nice vid !

[@ArjanCodes]

Thanks so much Georgi, glad the content is helpful!

[@BryanChance]

Is this a new concept to Python? I like playing around with programming languages as a hobby. Is this like using delegates or overloading in other languages like C,Java, or C# but specifically for "data"?

[@galanu]

Arjan, could you please do a video on best practices using @dataclasses and databases. When to use, when not to use. Thx

[@ArjanCodes]

Thanks for the suggestion!

[@yiyangzhang608]

very practical and useful, help me a lot, thank you🍗

[@91F2Z]

Minor confusion...you use "slots = (min.timeit..." which seems that you are using the reserved word 'slots' as a variable name?

[@simonetheditch809]

Love the way you teach. Would be so much appreciated if you can make a similar course in C++

[@denissipchenko2455]

As far as I understand, you can't use @dataclass(frozen=True) together with __post_init___ Error on 13:28 - it can't create class itself because of _search_string, not because of person.name change...

[@markdatton1348]

Could you also simply create your own function to supply to the dataclass definition, say create_empty_list() that just returns an empty list, and have it achieve the same thing? Is there something specific about what the field() function does?

[@DrorF]

13:30 It seems like the error is due to the assignment in the initialization of the object (assignment to "_search_string" in "__post_init__"). I encountered the same problem, and was baffled why it didn't work for me, but then I noticed it didn't work for you either. It seems that you cannot do it even in the initializer ("__init__"). You can hack your way around it by doing "object.__setattr__(self, '_search_string', f'{self.name} {self.address}')".

[@DustinHenryOffutt]

brilliant. thank you sir

[@ArjanCodes]

Glad you enjoyed the video!

[@yousefsadeek6640]

if that really what u want well there is so many modes developer want and modes most the cases mean low level language implementation (another whole dimension not implemented of the language) and I think u have an idea what that mean from security and the language pattern perspective and proof that u don't make any conflict, it just so expensive remember that their company tag is "you only need python and a little of c code" before u make a think about the python lang cause that how they (python org) offer themself and thnakes for the video u did a great good ☺♥♥♥

[@sfbuck415]

"Ture" oops, good to know I'm not the only one making that mistake. if you wanted to do high performance data crunching wouldn't it be better to use native code?

[@KangoV]

Nice video. I tried to do STIX deserialisation/serialisation with Python data classes. It came out being ~40x slower than java!. STIX is a very complex specification from Oasis (~300 pages). Hmmmm. I really want to like Python, but it's just so damed slow! It kinda explains why it uses so many C/C++ libraries as dependencies.

[@vitharana1996]

Nice explanation!

[@ArjanCodes]

Glad it was helpful!