Metaclasses in Python

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.

CONTEST WINNERS (CONTEST ENDED 10/9/21) :
PyCharm: Yannick Kuhn, peter duffy
CLion: BalkanSwine, Laurin Neff

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CHAPTERS
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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

[Ganerrr]

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

[andrewglick]

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

[QuantumHistorian]

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

[pericofalcor]

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

[macchicken]

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

[foxcirc]

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. 👍

[yogachen]

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

[dragon_pi]

"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

[mytelevisionisdead]

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

[brucewayne]

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

[rafaelhdebarros]

This is a terrible idea, super slow, and very very dangerous.

I absolutely love it.

[MathMagician]

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

[jaysonbunnell]

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!!

[Chris-ywis]

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

[samuellebot]

this is heresies, black wizardry and demonology combined

[dariuszspiewak]

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.

[lawrencedoliveiro]

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

[UntakenNick]

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.

[nhoover]

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

[secozzi]

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