Metaclasses in Python

Рет қаралды 147,553

Күн бұрын

Metaclasses customize the class creation process.
We go over what metaclasses are and give some notable examples, including: abstract base classes, adding function overloads, and dataclasses or code generation.
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― mCoding with James Murphy (mcoding.io)
Source code: github.com/mCodingLLC/VideosS...
Python metaclass docs: docs.python.org/3/reference/d...
Previous video on new: • __new__ vs __init__ in...
Another great metaprogramming video: • Python 3 Metaprogramming
Python descriptor docs: docs.python.org/3/howto/descr...
Python ABC docs: docs.python.org/3/library/abc...
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CHAPTERS
---------------------------------------------------
0:00 Intro
1:28 What is a metaclass
3:58 Simplest possible metaclass
4:59 Load time metaclass
6:08 Abstract base classes
8:03 Function overloads
14:10 Dataclass code generation
15:01 Giveaway instructions

Пікірлер: 824

@andrewglick6279 2 жыл бұрын

This video was so magical I'm tempted to call it a ___video___

@qkimat 2 жыл бұрын

Or a video of a __video__

@zoulei881027 2 жыл бұрын

5 letters are too long. use __vid__

@30IYouTube 2 жыл бұрын

Ah... *dunder video*

@boggri 2 жыл бұрын

magic, like a magic ___methods___ in Python )))

@tips1483 2 жыл бұрын

@@zoulei881027 yeah and the __str__ will return “video”

@GanerRL 2 жыл бұрын

i will literally never have a practical use case for this but it still makes me happy it exists edit: ok within a year I have used it several times I retract my previous statement

@tswdev 2 жыл бұрын

The answer is basically proper encapsulation. You can shift the complexity to the caller (outside the class) or you can keep it in the class where its manageable while keeping the caller (outside the class) simple. Creativity is everything and this is just another tool to support that.

@user-vt9bp2ei1w 2 жыл бұрын

I actually used Metaclass to modify the __iter__ method of my Enum class to skip some values. Basically like this: from enum import Enum, EnumMeta, auto class MyEnumMeta(EnumMeta): def ignore(Cls, e): return False def __iter__(Cls): return (e for e in super().__iter__() if not Cls.ignore(e)) class MyState(Enum, metaclass=MyEnumMeta): Empty = auto() A = auto() B = auto() C = auto() @classmethod def ignore(Cls, e): return e is Cls.Empty

@skully90 2 жыл бұрын

I used it all the time when I was a Java developer when I needed similar blocks of code to handle single item of type X or a list of items of type X. 99% of the time it was two functions with one function handling single item and the "overloaded" 2nd function handling the List of that item

@tochka832 2 жыл бұрын

dunno, i use overloads all the time in Nim and C++, its rather handy tool for segmenting code otherwise you would need to create a single function in python that has all the implementations depending on args* kwargs** signature which is rather clunky

@MrTyty527 2 жыл бұрын

@@user-vt9bp2ei1w crazy

@QuantumHistorian 2 жыл бұрын

7:55: _"No need to be confused"_ Me: Most confused I've ever been in an mCoding video #pycharm

@pericofalcor 2 жыл бұрын

Metaclasses looks very powerfull, unfortunately most people using "powerfull" features in a big codebase usually leaves the most powerfull mess to be maintained. Great video! #pycharm

@5h5hz 2 жыл бұрын

Hello! "Powerful" is spelt with 1 'l' not 2 :)

@royz_1 2 жыл бұрын

Well said

@pericofalcor 2 жыл бұрын

@@5h5hz Thanks. At least I was consistent.

@5h5hz 2 жыл бұрын

@@pericofalcor hahaha such a programmer response, I love it!

@ilyboc 2 жыл бұрын

He meant powerfull of poo poo

@brucewayne1777 2 жыл бұрын

I taught Python for 2 years at the university level. I thought I knew more deep wizardry than any person should know. After seeing this, it's clear that I know nothing. #pycharm

@matthieurochette 2 жыл бұрын

Same here, my friends call me when they have a question about Python because they know I love it and know it quite well, but when they call me a "Python master" I humble myself by remembering this channel exists :')

@macchicken98 2 жыл бұрын

My mind is blown. So many possibilities once you know what Python does under the hood. I would find it super interesting to learn more about how C-bindings like numpy uses them are built and how one could add them too. #pycharm

@pranavnyavanandi9710 2 жыл бұрын

How do you go about finding what python does under the hood, in a relevant manner?

@ganeshlakshmanan3391 Жыл бұрын

My mind is not blown as these features have been available in other OOP languages for ages. However I still like Python for its simplicity and would dread going into typing library, generics etc. I prefer simplicity.

@yogachen7885 2 жыл бұрын

This is the most complicated subject of Python I’ve ever seen. Thank you for your work. #pycharm #clion

@foxcirc 2 жыл бұрын

Since I've -lot's of work- nothing to do right now, I counted how often you've said the word 'class' and 'metaclass' in this video: *·* class ⟶ *62 times* *·* metaclass ⟶ *33 times* Oh my god, I watched the video on 2x speed and at 1:37, my brain just started to hurt. I really like your content by the way. There are so many useful python features I've hever heard of before. 👍

@mCoding 2 жыл бұрын

Do occurrences of metaclass also count towards class?

@photon6156 2 жыл бұрын

Don't worry, if you watch plenty of videos at 2x, you'll get used to it

@foxcirc 2 жыл бұрын

@@mCoding No, I counted them seperately, I counted things like "class body" though. Still 70 times seems like a very high number. EDIT: I counted again and updated the numbers, though not much changed.

@georgplaz 2 жыл бұрын

@@foxcirc was that "edit" a form of youtube commit message? 😁

@ciscoortega9789 2 жыл бұрын

I feel like your videos have given me a really deep understanding and appreciation of all the internal magic that goes on behind the scenes on Python. Thanks for the content!

@SystemfehlerK 2 жыл бұрын

All programming languages seem to converge towards each other. Combine this with Cython and static typing, and you just made a slower C++, but with more libraries. #pycharm

@chrisvinciguerra4128 2 жыл бұрын

As the world progresses more we all figure out the best way to do things has been C++ all along.

@duality4y 2 жыл бұрын

@@chrisvinciguerra4128 c++ is not a good choice for embedded systems c ftw

@supernoob0536 2 жыл бұрын

@@duality4y May aswell just hammer the opcodes into RAM yourself

@VivekYadav-ds8oz 2 жыл бұрын

@@chrisvinciguerra4128 Yeah that beautiful manual memory management when you're designing a high-level user-facing application was always the right way all along.

@mCoding 2 жыл бұрын

Gratz! You (Yannick) get a PyCharm license! Contact me to claim your prize! mcoding.io/contact

@mytelevisionisdead 2 жыл бұрын

Man the information density in your videos is mindboggling. Every 20 seconds there's something I'd need to sit an hour for to fully absorb the concept and the code. Well done, thanks

@jaysonbunnell8097 Жыл бұрын

one of my favorite things about python is how modular the language itself is. You can just overload anything you want, and having the syntax be so malleable is so fun!!

@theepicguy6575 2 жыл бұрын

This is actually that rare gem content found under the depths of the internet. Been trying to wrap around meta-classes for a week now, with so little luck. The docs/content revolving around such concepts are so scarce, But you made it so clear as day. Thank you :) -don't need pycharm cause VSC is nicer lol-

@Chris-yw5is 2 жыл бұрын

For once Python is making me appreciate the simplicity of C++ and not the other way around #clion

@kurtmayer2041 2 жыл бұрын

don't worry, we'll get reflections in c++ soon(tm)

@duality4y 2 жыл бұрын

@@kurtmayer2041 i need that

@nabeelsherazi8860 2 жыл бұрын

This is so much simpler than anything C++ reflection ever will be. At least this is consistent lol

@tochka832 2 жыл бұрын

simplicity... of C++? in what world is it true lol

@VivekYadav-ds8oz 2 жыл бұрын

You must've just started learning C++.

@legotechnic27 2 жыл бұрын

I've not used python in years, and primarily use TypeScript myself currently. I had an alright time using Python when I did, but didn't think too much of the language, but your videos including this one really make me appreciate python more! This whole system shown in the video is very elegant imo, and very powerful.

@secozzi2111 2 жыл бұрын

It's interesting to see overloading implemented in Python, I saw a stackoverflow comment suggesting to use multiple dispatch instead and now I might see why considering the slowdowns. Great video as always :) #pycharm

@dragon_pi 2 жыл бұрын

"the type of big A is a type but the type of small a is big A, whereby the type of type is type" That's exactly the feature you will probably not use for a long time, but years from now you will remember and it will save your life! Best thing about python, it's not like other languages where many base features are hard-coded, but you can customize EVERYTHING #pycharm

@georgplaz 2 жыл бұрын

its not always a good feature

@dragon_pi 2 жыл бұрын

@@georgplaz yeah, too much customisation just gets everyone confused, you cant replace every descriptive function name with some __magic__ and have people (and yourself) still understand it.

@UntakenNick 2 жыл бұрын

So you were trying to overload a function with the wrong syntax and didn't work, the you used the correct way to do it and worked. Mind bending.

@samuellebot4390 2 жыл бұрын

this is heresies, black wizardry and demonology combined

@Kenionatus 2 жыл бұрын

Every use of this forbidden knowledge needs to be marked with # Here be dragons!

@jezreel3584 2 жыл бұрын

I've definitely learned more from your channel than any of the other python channels, and courses I've taken combined. Please keep making such great content. #clion

@Pyroseza 2 жыл бұрын

James, every video I watch you blow my mind with what is possible in Python, I don’t know yet what I’ll do with all this new knowledge but dang is it fascinating! Thanks for the quality content #pycharm

@_gregor 2 жыл бұрын

Awesome video! It's a bit more advanced than usual, but it's good to hear something like that once in a while!

@mgdibtygd 2 жыл бұрын

Fabulous! Just what I needed to understand this shiny yet murky realm of metaclasses.

@deadmanbg 2 жыл бұрын

I'm really happy that you are making speed comparisons. This is something I often do with python, to figure out what works best, but I don't always understand why. #clion

@gideonfelt2819 2 жыл бұрын

Python gets more intricate and beautiful the more I use it. (and learn from your videos)

@dariuszspiewak5624 Жыл бұрын

David Beazley, as far as I remember, advocates the use of class decorators (where possible) instead of metaclasses. The decorators are easier to handle, easily composable and easier to understand. But sometimes... yes, one has to take the bull by the horns and dive into metaclasses (not for the faint of heart). There's no wizardry at play here but one has to go through a lot of theory and practical examples to really start to see (appreciate?) the structure and intent of the creators of the language. Thank you for the video and spreading the knowledge.

@turtlewasnttaken 2 жыл бұрын

This was actually quite interesting. I didn't know function overloading was even possible in python! Very cool. #python

@gawwad4073 11 ай бұрын

Your videos are very useful. Short and to the point and ofter cover subjects you may not encounter when using the language even professionally. Thank you!

@nhoover 2 жыл бұрын

Very clear explanation. After over 10 years of python programming I still learn new tricks from all of your videos. Thanks!

@mCoding 2 жыл бұрын

Great to hear!

@oxey_ 2 жыл бұрын

Yet another banger, I didn't even know this existed to be honest! Really interesting watch. As for the giveaway I 'm a student so I get their stuff for free, but it's actually incredible you got that opportunity from Jetbrains! Congrats on that.

@jachymmierva9453 2 жыл бұрын

This is extremely interesting. I tried to learn about metaclasses about two years ago, but I didn't understand it - until now. Excellent explanation.

@mCoding 2 жыл бұрын

Great to hear!

@mirage3dee 2 жыл бұрын

Very interesting information there. I would think, though, that most people have gotten around not having overloads built-into standard Python for so long, that normal Python paradigms suffice for all their coding. Overloading is nice to have, but I think it's more of syntactic sugar to other possible syntaxes. Somehow I can't help but think about the Zen of "Explicit is better than Implicit" might apply here as well, especially when usage is coupled with non-keywords args. Thank you for the wonderful videos, and I must admit this is my first comment on your channel, but I follow your videos constantly. #pycharm

@wizardfix 9 ай бұрын

This is really fascinating stuff James! I thought I was pretty experienced with Python, but you are helping me take my understanding to another level. Many thanks for sharing your wisdom.

@mCoding 9 ай бұрын

Hi Wizard, thank you very much for your kind words! I'm glad you enjoyed and glad to have your viewership!

@DanielLavedoniodeLima_DLL 2 жыл бұрын

I think the good part is that there are so many concepts you touch that I didn't even know in Python. I had to stop several times to look the documentation and learned a lot! Thanks! #pycharm #clion

@parlor3115 2 жыл бұрын

Damn, I've got to appreciate how flexible Python is. This is face meltingly awesome.

@mCoding 2 жыл бұрын

Thanks for the kind words!

@aaronm6675 2 жыл бұрын

Great video, i had no idea these aspects where so customizable!

@andrewhicks 2 жыл бұрын

Amazing. I’ll definitely be needing to watch this vid again a few times to understand it, but it’s truly mind blowing what you can do with metaclasses. #pycharm

@l4luchi123 2 жыл бұрын

Loved the part where you showed what's behind the curtain of some standard libraries. You should make a whole series of this. 👏🏻 #pycharm

@lawrencedoliveiro9104 2 жыл бұрын

7:33 This is how the enum module is implemented -- you create enum classes by subclassing base classes that have a special metaclass attached.

@mattnorth84 2 жыл бұрын

Being a beginner with Python I'm quite happy I managed to follow what was going on here. Even though the approach discussed here has various negatives the content as a whole was quite informative. Thank you. #pycharm

@spaghettiking653 2 жыл бұрын

Thanks sir, your content is always enlightening. Frankly, it sometimes stupefies me how much there is to learn about a language that many of my friends, and my computer science teacher, dismiss as simplistic... great content as always! #pycharm

@mCoding 2 жыл бұрын

Glad to hear that! It never ends, I learn many new things every day! Sometimes in the process of recording :)

@VivekYadav-ds8oz 2 жыл бұрын

Seriously, if this language had tricks up its sleeves to do a lot of this at compile-time (like Zig), it would've been the most powerful language across the domains.

@VivekYadav-ds8oz 2 жыл бұрын

I mean seriously, so easy to pick up and get started, yet so accessible to dive deep and get lost into the wild wild technicalities.

@matthieurochette 2 жыл бұрын

@@VivekYadav-ds8oz You can look into JIT compiling solutions for Python like numba (library) or PyPI (interpreter) for example, it lets the code be compiled at runtime (which slows down the first function call, but generally makes the next ones way faster, catching up to the realm of fully compiled languages)

@CHROMIUMHEROmusic 2 жыл бұрын

@@matthieurochette Yeah numba is awesome!! Relatively simple to use as well

@alexismandelias 2 жыл бұрын

Every time I think I am quite knowledgeable in python a new video is posted and I realize how few features of python I actually use

@jakubzurakowski8815 2 жыл бұрын

I probably will never use Metaclasses personally, but it's great to know that they're there and what they do! #pycharm #clion

@herogpi1 2 жыл бұрын

Never thought we could define two functions with same name but receive differents parameters, like I was used in C++. That's very nice! #pycharm

@bnev 2 жыл бұрын

Your videos are so impressive, very good explanation and really clear examples - for real you are a cut above the rest in this space and I'm glad your channel is growing so quickly! #pycharm

@thinkingforyou8421 2 жыл бұрын

This was amazing! I was just wondering if there was a way to do this in python. I didn’t even know metaclasses existed before now. Thank you for the very detailed explanation! Keep it up! #pycharm

@pavolkollar7748 2 жыл бұрын

Damn. The type of video to really smack you in the face, when you think you know programming. Do more, James, your content is fantastic! #pycharm

@lxathu 2 жыл бұрын

Now, that we've learnt about this from this fantastic video, probably it's time for the designers of the language to learn, from the very same video, that the most basic feature of am OO language should not be paid in blood.

@mCoding 2 жыл бұрын

Haha you're welcome to suggest but I think the designers are mostly against checking types at runtime. Also they will tell you python is a multiparadigm language, not just OO!

@FranziskoGomes 2 жыл бұрын

Thank you for your dedicated work, James Murphy. This video proves it once again. #pycharm

@mCoding 2 жыл бұрын

My pleasure!

@ErikS- Жыл бұрын

Excellent video. It took me some time to understand it, but it is pretty genius what you do. I saved this video because of it being so valuable... I see that your example implementation that allows function overloading, indeed causes a big amount of overhead. Maybe its an idea to raise a PEP for getting a real solution that allows us to overload functions in future version of python. Because honestly, I think it is a very worthwile addition to python.

@rafaelhdebarros 2 жыл бұрын

This is a terrible idea, super slow, and very very dangerous. I absolutely love it.

@mCoding 2 жыл бұрын

You had me in the first half

@philippedias4357 2 жыл бұрын

At least a clear and also deep explanation of metaclass mechanism and some uses. Not sure I will ever use it since changing much class behaviour makes code difficult to maintain. Thanks man. #pycharm which is my favorite IDE for python.

@gregh6586 2 жыл бұрын

James Powell had a great talk at some PyData which included metaclasses though your introduction is much more practical. Nice one! #pycharm

@yuli3873 2 жыл бұрын

My favourite programming channel

@calvindang7291 2 жыл бұрын

This stuff is super cool. That function overloading still looks like black magic after you explained it. #pycharm

@chandramgc 2 жыл бұрын

WoW !!! Metaclass are overwhelming. But they are quite amazing. And really like your efforts in teaching these concepts to us. This is the most interesting KZfaq channel out of all my subscribers #pycharm

@jurgen6706 2 жыл бұрын

I always wondered how these abc classes worked specifically. Thanks! #pycharm

@mCoding 2 жыл бұрын

Glad it was helpful!

@HeyImAK 2 жыл бұрын

I feel like this channel both teaches you advance python and the foundations you didn't know you don't know. Thanks! #pycharn

@Kuk0san 2 жыл бұрын

I remember stumbling upon this concept once and wrote some magical shit that even I couldn't parse after the fact, but it worked like a charm so we went with it... If I could track down the code I bet I could understand it better now, thanks for the deep dive! On a side note, abstract base classes are one of my faves, love making use of them #pycharm

@squintingwhale 2 жыл бұрын

This topic was something I've been wanting to understand better for a while! #pycharm

@svenvancrombrugge9073 2 жыл бұрын

This was pretty mindblowing...

@kpuano 2 жыл бұрын

I gave up trying to understand metaclasses before, but with your video I could get a good grasp of it even though I had to watch some parts twice or thrice (so many concepts). Thanks! #pycharm

@MrTyty527 2 жыл бұрын

learning these bits of lower-level mechanisms in Python lets me understand how Python magic works, especially for those built-in decorators like property. #pycharm #clion.

@srijanmukherjee4658 2 жыл бұрын

and yet again, I feel like my python programming skill has leveled up. #pycharm Some more C/C++ content would be great.

@ObserverZero 2 жыл бұрын

Great video on how to be taken out back by your team and shot.

@thatinstant 2 жыл бұрын

Even after watching this video, metaclasses still seem magical. There's no end to what you can do with them. #pycharm

@markasiala6355 2 жыл бұрын

Even if I don't make use of metaclasses anytime soon, the deep dive into the how classes work in the background has been very interesting. #pycharm

@salmanshah4512 2 жыл бұрын

I have used metaclasses before but I never realized you could do this much with them. Very eye opening #clion

@sultanapsalamov9309 2 жыл бұрын

I'm currently trying to apply the strategy pattern in python, so such a detailed explanation of metaclasses is very useful. Thank you. #pycharm

@Hecticam 2 жыл бұрын

Wonderful video full of examples and use cases to explain this advanced function! Looking forward to your next one! #pycharm

@NovaGamma_ 2 жыл бұрын

It has been a long time since I was really lost while watching one of your video. Absolutely didn't expected that. #pycharm

@cemsity 2 жыл бұрын

Metaprogramming and Reflection might be a little over my head, but this is way easier to read, than other methods for python overloading even if it does cost some time. #pycharm

@huantian 2 жыл бұрын

I have no idea what's happening but it works and it's cool!

@TheAlcalda 2 жыл бұрын

#pycharm #clion You shed some light onto these Metaclasses - I always avoided those up to now. But now I got some weird ideas, though. I really like the way you get into these deep details of the language.

@tyto.c 2 жыл бұрын

absolute madness, the great old ones will be impressed #pycharm

@dylanthomas7446 2 жыл бұрын

Been using abc for awhile, and it's super interesting to know how it operates under the hood. #clion

@TheGreatAkhillis 2 жыл бұрын

Well that's the first video that I watch on your channel that left me puzzled yet excited to watch it again #pycharm

@mCoding 2 жыл бұрын

I'm sure you are in good company, metaclasses are probably the most difficult thing to master in Python. Master metaclasses and you can master the whole language!

@virtualraider 2 жыл бұрын

@mCoding would a set be a better structure than a list to keep "seen" parameters? In a list you'd run the risk to overload more than once with the same arguments. Unless you want to combine overload and duck typing? 🤯

@davidhaggiag 2 жыл бұрын

I learn something new with every video you post, thanks. #pycharm #python

@sadhlife 2 жыл бұрын

"a class defn is actually just syntactic sugar for calling a type constructor" There's a tiny caveat here, like being able to pass kwargs to the type definition's bases, which can't be done with `type`. To be able to do that you'd have to use `__build_class__()` instead, so in python3 (i believe starting from py3.1) it's actually sugar for the build class top level function instead. It's nothing major though, but I think if you're making an absolute statement it should be correct.

@TheoCJnr 2 жыл бұрын

Consistently high quality content. Well done James! #pycharm

@elianangius6465 2 жыл бұрын

Awesome under-the-hood demo implementation of Python’s missing overload OO functionality. #pycharm

@TheFlo624 2 жыл бұрын

I have always wondered what metaclasses are used for. Thanks a lot! #pycharm

@friedkeenan 2 жыл бұрын

Yeah, metaclasses are super powerful but also something you should think hard about as to whether they're the right tool for the job. For the purpose of function overloads, I'd probably even say they're not the correct choice, and would just be better just as a property-like decorator where you do @overload for the first definition and then @f.overload for the subsequent definitions. And of course there's the question of whether having overloads in python code is even good

@arciomdaniuk 2 жыл бұрын

Great video. Sometimes it's hard to understand such deep diving into python but I'm trying to do my best. Also it's big pleasure for me to see such videos on KZfaq. Thank you! #pycharm

@jma42 2 жыл бұрын

Man, I might actually try making a cool library that can be used in my fav game, metaclasses are so cool

@yolosaurusrex90 2 жыл бұрын

been enjoying your videos. i think youtube has a plethora of beginner level content but not enough intermediate to advanced. you're hitting a sweet spot with these videos. #pycharm

@Friedrich713 2 жыл бұрын

The metaclass overload reminded me of monads from functional programming - essentially 'something' that gets treated differently based on its properties. Very neat! Oh, and... #pycharm :)

@hjewkes 2 жыл бұрын

This was absolutely fascinating. I’ve been using ABC meta for ages but didnt know how it worked under the hood #pycharm

@qsykip 2 жыл бұрын

Once again you’ve created a short yet excellent video that I’m going to spend hours replaying and pondering over. Thank you! #pycharm #clion

@mCoding 2 жыл бұрын

My secret plan for increasing audience retention :)

@zactron1997 2 жыл бұрын

I'd love to see a short followup to this concept using the new Python Match syntax, I don't imagine it drastically changing performance, but I could imagine it allowing for a much cleaner code base.

@SophieJMore 2 жыл бұрын

Wow, my mind is literally blown. Would be cool to see a video on weakref some time in the future. #pycharm

@MatthiasStuebner 2 жыл бұрын

Now my mind isn't less bend than before, but I guess when I watched this video 100times it might get better. Thanks for the video. #pycharm

@slava6105 2 жыл бұрын

Wow! definitely high potential in overload

@SeanNicholsEh 2 жыл бұрын

Well. That was... mind-bending indeed! Not so much the usage (that was pretty straightforward) but all the details and digressions in the implementation. I always follow along with these videos in my python interpreter, so I can pause the video whenever I'm not certain about something, and play around a bit until I'm sure I've got it, then resume the video. Normally that only adds a few minutes here and there, but this video took me -- I kid you not -- OVER THREE HOURS to get through due to all the times I had to pause it and work out what was going on, not to mention all the scrubbing back and forth to refer to an earlier part of the video, unwinding the code as I went, to understand exactly what was being passed around in a later part. ANYWAY. I think I mostly have it straight now, with one glaring exception: At around 11:23 on line 64, you throw 𝚔𝚎𝚢: 𝙾𝚟𝚎𝚛𝚕𝚘𝚊𝚍(𝚟𝚊𝚕) into the 𝘰𝘷𝘦𝘳𝘭𝘰𝘢𝘥𝘦𝘥_𝘯𝘢𝘮𝘦𝘴𝘱𝘢𝘤𝘦 dictionary. But I don't understand how the instance of Overload gets its __𝘨𝘦𝘵__() method called when it's an element of the dictionary? I would understand if it were an attribute of some class object 𝘢. Which is to say: let's assume we have an instance 𝘰𝘷 of 𝘖𝘷𝘦𝘳𝘭𝘰𝘢𝘥. Then if 𝘰𝘷 were an element of 𝘢, accessing 𝚊.𝚘𝚟 would for sure trigger a call to 𝘢.𝘰𝘷.__𝘨𝘦𝘵__(). But if you have 𝘰𝘷 as an element of a dictionary (let's call it 𝘥) which is in 𝘢, then accessing 𝚊.𝚍['𝚘𝚟'] would presumably only ever trigger a call to 𝘢.𝘥.__𝘨𝘦𝘵__()? So how does 𝘢.𝘥['𝘰𝘷'].__𝘨𝘦𝘵__() ever get called? I'm guessing that it's some magic behind the implementation of 𝘵𝘺𝘱𝘦.__𝘯𝘦𝘸__() ? Do elements of the namespace being passed to that function get transformed into attributes of the class being created? Or am I missing some other intuition here? Other than that, well... I am... enlightened!

@mCoding 2 жыл бұрын

Wow! I'm so happy to hear that you follow my vids to closely, this is surely the best way to learn! Indeed it is some magic behind type's new method. type.__new__(mcs, name, bases, namespace) basically eats the namespace argument and turns a wrapped copy of it into the new class's __dict__. So when I pass the overloaded_namespace in that spot, the overloaded_namespace essentially becomes the class dictionary for the newly created class! So you guessed exactly right!

@SeanNicholsEh 2 жыл бұрын

@@mCoding Aha! Awesome. Thanks for the confirmation!

@dominicgasperini9553 2 жыл бұрын

once again, more top notch python content!! would love to hear you share your knowledge of complex topics for other languages too! #clion

@sirbasspriester1838 2 жыл бұрын

I always enjoy ways of bending the rules like this! #pycharm

@tHe0nLyNeXuS 2 жыл бұрын

Really neat! Just a question: why not use a dict of signature hashes resolve the best_match? I feel like it would be faster than iterating over the list of signatures.

@kurtmayer2041 2 жыл бұрын

just saying, you can (and i have) implement run-time overloads with just function decorators (which makes it also work on module-level functions)

@mCoding 2 жыл бұрын

Would love to see your implementation!

@NikolajLepka 2 жыл бұрын

a perhaps more efficient way to do overloading is via monomorphisation instead of having one key having a list of possible values that you then need to search through, you instead create a new name for each method based on its argument list and create a method called something like "f_int" and "f_string" and "f_any_any" as the names doing this lets you take advantage of the dictionary's fast lookup without being also limited by the list's slow lookup

@godofnothing520 Жыл бұрын

No, function overloading improves readability and avoids remembering too much function. Instead of having multiple "f_int" and "f_string" and "f_any_any". It is better to only have 1 "f" function to handle all arguments.