5 Tips For Object-Oriented Programming Done Well - In Python

You can do Object-Oriented Programming badly, or you can do it well. Especially in Python, there are many ways to trip up. So, here are 5 tips for Object-Oriented Programming done well.
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🔖 Chapters:
0:00 Intro
1:14 A bit of background
3:01 #1 You can combine FP and OOP
5:16 #2 Make classes either behavior-oriented or data-oriented
7:24 #3 Be careful with inheritance
10:22 #4 Use dependency injection
13:32 #5 Don't abuse Python's power features
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[@ArjanCodes]

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

[@MistaT44]

Mid level engineer here. Binge watching your videos like its netflix. Hands down some of the best programming content on youtube. Thank you!

[@ArjanCodes]

Glad you like them!

[@Golgafrincham]

Really nice video, thanks a lot! Got a project at work with a lot of inherent complexity about a year back and would be completely lost without all the stuff I learned from your videos. The great thing is that every time I watch a new video I get new ideas on how to improve things!

[@MedievalChips]

I love your style of writing code it makes sense and it's clean and organized. Keep them coming. I am actually trying to adapt my code style to be more like yours as I like it so much.

[@allo5668]

This is a great topic! I'd like more like this, a general list of hard-earned tips that have marinated in an experts mind for a long time

[@iNuchalHead]

Good stuff. Separating data and behavior concerns is forward thinking. Not being worried about strictly adhering to a design paradigm is so refreshing to hear; let's be practical! This is your best video, yet!

[@neematsering4017]

I can't believe your channel hit 100K+ subs. I have learned a lot from you Arjan, thanks for all the quality videos (and free knowledge). You deserve more.

[@samleheny1429]

Tip #2 is one of the most helpful pieces of advice i've come across. Applying that thinking to my classes has made my projects way more organized.

[@evangelossyrmos9576]

One of the best videos I've ever seen on OOP, so simple but with all the necessary insight for future development!!!!

[@chaddrobertson5805]

I've found myself incorporating many of these naturally over time as well. My use of inheritance is still something I should work on - I often just slap it on hastily because its easier (at the time), but it definitely makes for some readability issues down the line. Another fantastic video, thanks!

[@CottidaeSEA]

Inheritance is good if you have some base data that all similar classes should share. I don't believe methods should be inherited. In that case it should be abstract methods which need implementations, but work under the premise that "these are required to work". That is in my opinion the most sane way of using inheritance. At my job, there are some massive inheritance issues, where one class might have three ancestors through inheritance. It's honestly awful, but it's basically something that people who knew how to write code but not structure code made, and now we're suffering from the consequences much later. We're working on modernizing the code base and improving it, but we'll still be left with a lot of legacy code.

[@pettypenguin656]

Consistently good videos covering topics in a sensical way with examples reasonable enough to be relatable but not overly complex for explaining the subject matter. Great job. Would love to see you make some more "difficult" testing-related videos dealing with concepts like async sqlalchemy sessions and the many other difficulties that arise with testing asynchronous code. It's one of the areas where I feel least confident and most "Google a lot of stuff until things begin working" and I'd like to get away from that feeling, but it seems resources surrounding these topics aren't great currently.

[@twentytwentyeight]

Oh this was the catalyst, it finally clicked. Thank you for such curated, intentional explanations. I aspire to be as engaging and well-informed one day.

[@NGrimthrie]

I find that because these OO principles are abstract, they take quite a bit of repeated exposure to "see" in day to day coding. Especially when starting a feature from scratch. Thanks for making such a variety of videos about them (including the course). It's really helped keep the reinforcement learning/repetition fun and interesting.

[@DeKeL_BaYaZi]

the understanding of separating the data classes and the behavioral classes in such a clear way is really amazing and an awesome idea which I will most certainly implement and take into consideration with every OOP step I take. thank you so much!

[@betoharres]

this is quality content for senior devs; you're talking about abstract topics that matters on the big picture/decision making of big projects; I loved it, subscribed!

[@ArjanCodes]

Thanks Alberto, and welcome on board 😉.

[@nostromo9081]

I'm making my way to senior and I would dare say you helped me a lot with getting to a whole different level of app design. Thanks

[@Pawl0solidus]

Amazing video Sir! Thank you very much for sharing your expertise with us! I always learn a lot from you!

[@sep69]

Thank you for another interesting video. It think is filmed really nice also. Visually pleasing, calm, colourful and still focussed on the code. Thanks again :)

[@1oglop1]

Thanks, I used the dictionary as a collection of functions/objects a lot but until this video, I did not realize that enums as keys can work really nice.

[@marcotroster8247]

I did all your tips in my last refactoring and it's working wonders 😂 A sane combination of functional and oop is actually great for writing well-structured code without crazy side-effects! 😄 One thing about turning behavior-oriented classes into raw functions: If you wanna do dependency injection and duck typing via protocols, it's really essential to represent your set of functions as a class because it's way more cohesive than passing each function separately (really helps readabity). And moreover something like attributes is necessary to store the handle to each dependency instance. But for the rest of the video, I totally agree 😁

[@bulelanibotman]

The dependency injection topic was something new to me, so thank you!

[@jett_royce]

I've worked in crazy spaghetti codebases, and architecture astronaut code mazes. After those experiences, I love this practical, real-world advice. Thank you.

[@ArjanCodes]

You're welcome - glad you liked the video!

[@augustusbatilojibba1405]

Love ur tips. The helped me a lot. Please make a full course for us

[@ArjanCodes]

Thanks Augustus! There actually is a full course: www.arjancodes.com/mindset ;).

[@nathanrasmussen931]

You have the best videos on python and coding on youtube. You put in a lot of work into your videos and they are to the point and amazing every time. Thank you!!!

[@ArjanCodes]

Thank you, Nathan! I'm really happy to hear you enjoy the content.

[@fabhi]

Rocking that shirt! And as always concise and wonderful video

[@cheebadigga4092]

About inheritance: One more usage of it is for making C/C++ classes integrate better in a Python program. Depending on how the C/C++ side is implemented, inheriting from these, or creating a class to wrap around them, might actually benefit the simplicity and readability of your code.

[@tir0__]

Wow 🤩 luckily I landed on this channel and loving it . Gonna go through each of the videos , amazing way of teaching

[@ArjanCodes]

Hi Priye, I'm glad you're enjoying the content - welcome here!

[@elkasmiadnane]

as someone who uses python for over 2 years now . This is a huge added value for a 16 mins video.

[@alanjames8085]

Love this video and all the videos on your channel. Super helpful❗️😃 I would love to see an equivalent video on # Tips for Functional Programming in Python 👍😃

[@Laflamablanca969]

The python community has no concept of OOP. Your channel is honestly the first I’ve ever found that actually utilises OOP and is good at it. Keep it up my friend!

[@gustavojuantorena]

Great topic and thank you for share your knowledge

[@rodrigo2112-]

Great video Arjan thanks! I really appreciate your insights and the quality of your videos. I'm a developer with 20+ years of xp and I'll work with python for the first time soon and your videos are helping a lot on my preparation to be more pythonic.

[@ArjanCodes]

Hi Rodrigo, thank you and glad to hear you enjoy the videos and that they're helpful to you!

[@whkoh7619]

always great to see a video Arjan!

[@ArjanCodes]

Enjoy it :)

[@FORGIVE123N]

Excellent video about how to make the code cleaner and neat. Thanks a lot!

[@ArjanCodes]

Thanks so much Viktor, glad you liked it!

[@budoray]

I moved from C++ to Java in 96. OO was the bible. Things changed when Dungeon Siege released and ECS came to the forefront in my world. Had to go back to OO when DI tools like Hibernate and Spring became popular. I am retired from software development now and have come to Python late. Love your explanations. Most especially when it comes to inheritance and when to choose 'has a' over 'is a'.

[@tekno679]

Thanks for giving this great advice for free

[@broken_arrow1813]

I like you content on Python. You really know how to synthesize complex concepts into easy to understand bits. Do you have any material on react?

[@getpoked101]

Watched this with the team at work today. Good stuff

[@ArjanCodes]

Thanks, glad you liked it!

I'm kinda new to python, and tbh I see a lot of code that people say it's "more pythonic" that for me is just more complicated to read. I've seen some list comprehensions that look like RegEx and took me a second to understand. And a lot of what you talked here reminded me of how Django works, using classes (models) for data and mixing it with functional programming for views (even though you can use classes for views also).

[@johncrunk8038]

I wish some of the library writers would watch your videos. I have run across libraries that try to be a complete application and have such convoluted object structures that I sometimes end up writing my own library. Yuk! Keep up the great work.

[@oluwabukolaowoeye9898]

wow I loved every bit of this videofrom the introduction to the end, as a self taught software developer in the making vidoes like this helps a lot, I did not only like but i subscibed.Thank you

[@ArjanCodes]

Thank you so much, glad to hear you liked the content!

[@codeshowbr]

Great video, I am not sure if what you call Dependency Injection is not just "composition", I think of DI as a more implicit/automated process, just like Pytest does with fixtures and FastAPI does with depends

[@zdzichuWentyl]

i'd very likes your approach and sharing knowledge thanks for you good tips

[@apefu]

Lovely video! Could you do a video on Method Chaining? I've been told that it is not considered very pythonic. I've never found any good explanations as to why, though. It obviously works, and it is in plenty of libraries, so.. is it bad? Personally, I love it.

[@dawid_dahl]

Thank you! 🙏🏻

[@jordanmungo917]

This is a really good video. Only thing I'd say I disagreed with is separating classes by data vs behavior. In theory this sounds nice, but when I get into a larger project I almost always need some of my data focused classes to be able to do some various behaviors. I think separating those out too much from each other could pose other problems. All about balance though

[@swadhikarc7858]

Great topic indeed and looking forward for many such

[@ArjanCodes]

Thank you, glad you liked it!

[@jefralston]

Arjan, I love all your videos. You are a great teacher. I know it's not the focus of your video, but can you tell us how you have your line numbering setup in VSCode?

[@barrykruyssen]

code MUST be readable by humans first, has been my motto for years. And what you're saying is along those lines. The more I watch of your videos ,the more I like. I'm trying to "bing" watch your videos but my head feels like it may explode. 🙂 Keep up the good work.

[@cgreek]

Now this crack, is just unreal! Thanks for that ;)

[@orangeprogrammer]

Thank you for making this video. Great advice.

[@ArjanCodes]

Glad it was helpful!

[@Colaholiker]

I can see how Java gets a lot of heat for how things are done. When I started studying computer science in 1999, no surprise, Java was all the rage. Fortunately I had worked with Delphi before (a natural step up from my Turbo Pascal days in DOS), so I was able to tell apart what disadvantages are specific to Java and what to OOP in general. I have moved away to mostly working in C nowadays since I work as an embedded developer (never done C++), but I use Python for tools that make my life easier. That's why I watch your videos. When appropriate, I sometimes follow a semi-OOP approach in C, where I define a struct holding all data of that "object" and pass this (well, a pointer to it) to various functions that work on this data, much like the self parameter in an object's method in Python. I even call the parameter "self" most of the time. 😅

[@zacky7862]

Great tips again teacher!

[@jfsaraceno9265]

You must have access to my yt search history because this is exactly the video I need right now.

[@cantis]

Really good video, learned lots! Now I need to find out if you have a video on Protocols?

[@yevseldev]

I'm glad I found this channel

[@SolidBuildersInc]

Thank You, From the Functools to DataClassess and now blending (F and OOP). I feel this could have been your 7 steps pdf for download, lol I had a question about assigning a index in lieu of self generated indexing. There are (Cluster, Multilevel, Sparse, Hash etc.) I have a establisd mathematical function I would like to use to assign a index to the database instead of building out table relationships. I believe your depth of understanding of how to remain scalable and dynamic in your approach to coding gives me a bit of confidence that I can do something along these lines. Thank you for your valued insight in this field. My question is how can we have a discussion ? My bread just came out of the toaster, and butter must be applied for the best Bread in the WORLD, lol P.S. also my thumbs are cramping from this texting. I need to use VOIP more often.

[@coderider3022]

As a c# oop dev, i think your points are good and the way I approach engineering with my python.

[@sbonventure]

Great video! I'm not exactly sure what you meant by an abstract base class you use for inheritance, but I like to use certain modules, from pypi or from Python to manipulate those objects and localize my own objects. For example, creating a Paddle Class in a pong game that inherits from Python's Turtle. This way all of the code for those objects is in one class instead of riddled around the code. Inherit a turtle from Turtle and create your own custom turtles sort of thing. But maybe you said that in your video talking about inheriting from the Charge Class. I really like the idea of separating behavior from data in more complex programs. I like to see similar code in the same spots.

[@grantwilliams630]

Data classes have brought way more OOP to my code. A series of transformations on an object with predefined values is way easier to track compared to a dictionary

[@ndiegow1]

Great video!

[@Hubert4515]

thanks for the tips

[@estevaofay]

How do you feel about Dependency Injection increasing the number of inputs? On Clean Code it is mentioned that we should minimize params because we are just creating complexity by having to test multiple inputs generating multiple outputs. Wdyt?

[@Zillamakilla]

100% working THXs

[@sick000fight]

you can use ide to navigate embedded classes, interfaces or abstract classes...

[@TechieGuy82]

Superb tips.

[@Eltopshottah]

I like your explanations

[@dariuszspiewak5624]

The best strategy in life, not only in programming, has been expressed once in an interview with Bruce Lee. He said one should study martial arts (not just one) and from each of them take what works for one. Take it and from then on develop it. This is by far the best advice one can give in any walk of life: Take the best out of it and develop from now on. Therefore mixing different styles of programming should be standard, not something frowned upon. After all, a hammer is not the answer to all questions, so to speak.

[@AndreaDalseno]

Awesome, as usual. In my opinion the audio quality changed with respect to previous videos (and it was not an improving for me; previous ones were better).

[@Julie9009]

I loved the video, but the constant rustling sound is quite distracting

[@sjmarel]

Excellent tips

[@Brlitzkreig]

I love your teaching style. It's great

[@ArjanCodes]

Glad you’re enjoying the videos!

[@Han-ve8uh]

1. 7:07 you mention PaymentProcessor could be a module. When would you write a class as a module? Would the api_key then be a module scoped global variable? 2. 12:00 sounds like a reason to do dependency injection is so it's easier to test, are there other reasons? 3. It looks like we are polluting the function argument list when dependency injection pulls things from within order_food into it's argument list. What if we wanted to test more items, the argument list is going to grow to contain other business entities, as many as we want to test.

[@Ziggity]

This is seriously thoughtful stuff, I especially loved the part about not being locked into an OOP or functional style. It's always better to use the right tool for the job. What I didn't agree with as much was about classes being data or behavioral orientated. I always thought it was the other way around - that classes make more sense when you have data and behavior that are tightly coupled (say, a 2 year old dog playing fetch.) What do you think?

[@mateusb09]

Yeah, I agree with that. One of the main purposes of creating a class is being able to share the same common data across a lot of different methods. Splitting behaviour and data its kinda pointless for me

[@CottidaeSEA]

I'd say splitting data and behavior is useful in some circumstances. It can be a lot easier to have a class which manages such objects instead of the objects themselves doing all of the work. I'd say one of the primary reasons why you'd want to have methods in a data class is when it has data you don't want to expose publically. In which case I'd prefer if that method had an accompanying interface.

[@MrCreeeeeeeepy]

Thanks for sharing! What is the sound/track name at the end of the video ?

[@riptorforever2]

Best channel of advanced python OOP. thanks!

[@ArjanCodes]

Thank you, glad you like the content!

[@nowyouknow2249]

Superb! I am really enjoying your videos. Like seriously, however, Django has many inheritance in the source code. What can you say about it.

[@20dorko]

HI Arjan, thanks a lot again, this is great. Btw is the use of the Protocol in the 3.point basically the same if I would use abstractmethod from the ABC module and define the interface with it? What would be the difference in this case ?

[@legion_prex3650]

No, it is not. Protocol is just for static type checkers whereas an abstractmethod from ABC would raise an error, if a method wouldn't be implemented. The idea behind them both though is the same of course. Maybe, that's what you meant.

[@clauseclause6640]

Functional programming in not about using functions, it's more about stateless, function composition, memorizing, recursion and closures =) FP not easy to read and python is not great for FP. This video in more about procedure programming. When choosing between classes and functions keep in mind that under the hood python functions are just class instances with only (practically) call method :) I don't think it's a great idea to convert methods to functions, it could work, but you loosing internal state of class. And if your functions changes your classes state, or you have some global states - that's not FP at all =)

[@antebilic9259]

Correct it's a mixed style programming, with procedural and oo styles.

[@legion_prex3650]

you are completely right.

[@uniqueHandleName420]

algo boost comment. thanks for all your help!

[@bierviltbever]

The beard is growing. Arjan slowly turns into our spirital leader. Leading us through the deadly valley that snakes itself across the land of Guidotopia.

[@video-carl]

I enjoyed your video. In your tip #2, it would be useful to add an explicit "Why you create separate data and behaviour classes". It sounds like you are transitioning to FP when you say that often the behaviour classes could be replaced by a module of functions. Are you trying out any pure -FP languages?

[@DS-tj2tu]

Thank you!

[@ArjanCodes]

You're welcome!

[@ricardosuarezdelvalle4281]

What I tend to do is when functional programming makes more sense I put all the functions into a class that kindof describes what the group of functions does and make them all static methods or class methods

[@anandaputradoneva6665]

brother thanks for share this best Crack

[@sergheimarjin8184]

Would have been nice to also mention the terms "pure core" and "side effects". Especially the way the code should be organised. Haskel is probably one of the best examples. It allows I/O operations only in the "main" context. Hence all that unpredictability that I/O has is located in a "thin top layer" (easier to debug). The core must be immutable - the input gets transformed and returned at the output without any side effects. Same input generates same output no matter how many times that function is called. For dynamic programming languages there is also the PFAAO design pattern which is quite helpful. Writing tests for "pure" code is always a joy because it is really straight forward. Personally, I'm coming from more of a RoR background. Wouldn't say that Python is that great with FP. I think that Ruby does a much better job at FP but it has its own downsides (i.e: there are no native immutable data structures). After learning a bit of Scala, I was able to understand that 95% of the Ruby projects I've ever seen were done in a classical imperative way that mixes the stateful with the stateless and then gets really messy over time. PS: FP is a style. Can be very well achieved in any OOP language if FP principles are well understood and followed (ofc if we ignore the type system altogether which to me is probably Scala's best selling point).

[@MrPesto-gy2lt]

I would add: Use immutable data structures where-ever possible. e.g. dataclass(frozen=True) or tuple[Thing, ...] instead of list[Thing]. Do, if possible, not use a lot of getter/setter methods, but prefer to create new instances with the altered attributes. Immutability, delegation instead of inheritance, functional methods (no side-effects), and classmethod-factories that make the code easy to read and understand. Changeable class attributes are particularly a pain to test, because the control paths quickly factorize and become insurmountable.

[@ravenecho2410]

ive been using classmethods as a way to lock down interfaces, rather than using config files. especially when it comes to pipelines... good idea or bad? how would one use class methods? are they a replacement for a singleton?

[@BeesAndSunshine]

I wouldn't call data classes OOP and I wouldn't call any functions FP. Functional programming would be more about not mutating data class objects, not avoiding the usage of them. Functional programming would be writing functions that promise not to mutate their inputs if passed by reference, and don't have side effects that get consumed by external logic. I'm not advocating for a certain style, just want to make it clear that class != OOP and function != FP, the styles are more about the constraints you put on yourself and the patterns that emerge from doing so. They are not about using or not using certain constructs, though certain styles do tend to lean more heavily on certain constructs like a preference for tuples over lists (to give a Python example) in FP because they enforce certain principles.

[@Mr7Shane]

No, he used a function, therefore its functional programming. /s This has been the play of OOP for years. OOP used to be about so many things(encapsulation, inheritance, etc.). But now that all of those things have been shown to be terrible, its now just 'using classes/objects'.

[@Michallote]

@@Mr7Shane In my personal humble and very inexperienced opinion, Classes are the best single thing that allows you to store complex hierarchical data. Because you can have a very clear and defined level of control of what is stored in the class. And you can have the information you need not just as primitive types but as custom objects that enforce certain things about the data that simplifies managing them later. However behaviour oriented classes are so cumbersome and often feel unnecessary when you don't have variations of the methods (writing unnecessary preambles to each functions and such). So unless you need to define custom behaviour for each different object I would avoid classes all together in favour of funcions. Whst I like about Python is that it allows the user to do multiple paradigms without too much effort. Exploiting the advantages of different approaches and such

[@sherifahmed9286]

Awesome tutorial.

[@ArjanCodes]

Thank you!

[@junealexissantos4341]

my new favorite channel for python programming

[@ArjanCodes]

Thank you so much for the kind words! Glad you've been enjoying the videos :)

Awesome tips man. For me coming from non object oriented background I have always used a functional and object oriented mix. It just feels easier for some reason.

[@edgeeffect]

Modula-2!!! Kudos from a Pascal lover!

[@ArjanCodes]

Thanks so much, glad you liked it!

[@AnthonySherritt]

Thanks!

[@ArjanCodes]

Thank you so much, Anthony!

[@user-gc6bb1tk9h]

один из лучших каналов по теме

[@DistortedV12]

This guy does create a lot of object oriented code, sometimes importing a couple of functions in a python script is all you need

[@kenhaley4]

Arjan, I'd love to hear your feedback about a principle that I've used: That is, don't make a class unless you're going to need multiple instances of that class. I can think of one exception--a dataclass which has lots of instance variables. Otherwise, it seems like just using functions would be simpler. What to you tihnk? P.S. I love your videos. Your explanations are very clear and well thought out. Thanks!!

[@lyserigaud5828]

RRs7@2eaww

[@paulblart4551]

I love static classes because they make the code more readable and I hate not grouping my code

[@spicybaguette7706]

@@paulblart4551 You can also use a module. That's what modules are specifically designed for

[@stepanfilonov]

There’s a pattern called singleton which contradicts this principle. Most configs/settings you know in frameworks are singletons.

[@DinoDiniProductions]

Writing object oriented code well is basically a process of mostly avoiding object oriented programming

[@ronaldronald8819]

This sounded so familiar I did my (Sun)java certificates J2EE about 20 year ago. Retired now 🙂 yea i am old. Thanks for your insights.

[@erikgrundy]

My opinion's become that OOP isn't bad, there's just a lot of bad OOP code out there. A lot of the principles of OOP are sound, but they fall apart when you mindlessly apply them, and the same is true for FP. Someone who writes an AbstractSingletonFactoryFactory would also write some pretty heinous functional code, because the problem isn't the paradigm, but the person who applies the paradigm without thinking about their design first.

[@__brodul__]

I noticed you sometimes use the UML class diagrams to explain some OOP patterns (e.g. adapter pattern). I would love, if you would explain how to read those diagrams on some examples. I can't follow them in other videos.

[@ArjanCodes]

Thank you for the suggestion!