Python OOP Tutorial 2: Class Variables

In this Python Object-Oriented Tutorial, we will be learning about class variables. We will see how they differ from instance variables and also some ideas for exactly how we would want to use them. Let's get started.
Python OOP 1 - Classes and Instances - • Python OOP Tutorial 1:...
Python OOP 2 - Class Variables - • Python OOP Tutorial 2:...
Python OOP 3 - Classmethods and Staticmethods - • Python OOP Tutorial 3:...
Python OOP 4 - Inheritance - • Python OOP Tutorial 4:...
Python OOP 5 - Special (Magic/Dunder) Methods - • Python OOP Tutorial 5:...
Python OOP 6 - Property Decorators - • Python OOP Tutorial 6:...
The code from this video can be found at:
github.com/CoreyMSchafer/code...
✅ Support My Channel Through Patreon:
/ coreyms
✅ Become a Channel Member:
/ @coreyms
✅ One-Time Contribution Through PayPal:
goo.gl/649HFY
✅ Cryptocurrency Donations:
Bitcoin Wallet - 3MPH8oY2EAgbLVy7RBMinwcBntggi7qeG3
Ethereum Wallet - 0x151649418616068fB46C3598083817101d3bCD33
Litecoin Wallet - MPvEBY5fxGkmPQgocfJbxP6EmTo5UUXMot
✅ Corey's Public Amazon Wishlist
a.co/inIyro1
✅ Equipment I Use and Books I Recommend:
www.amazon.com/shop/coreyschafer
▶️ You Can Find Me On:
My Website - coreyms.com/
My Second Channel - / coreymschafer
Facebook - / coreymschafer
Twitter - / coreymschafer
Instagram - / coreymschafer
#Python

[@mtvcity2]

Your videos are more informative than my university lectures

[@coreyms]

Thanks a lot! That's a nice compliment. I'm glad to hear you find them useful.

[@silverzero9524]

and short and arent booooooring

[@MrZhunio]

This is so true. We obtain more information on those really short videos than we do in those long lectures on universities.

[@adityaverma6120]

True Story of every university

[@nicklesmatsch7588]

Well, kind of. In your videos we learn basically all the useful stuff we want to know, but in university we get all the side-information (sorry, no native speaker) we may find useful someday, even though we don't know yet, when it could happen.

[@trevorduncan7913]

it really makes a difference who teaches you.....it was wtf wtf wtf....then watch these videos...oh ya that's logical. you are an awesome teacher....please keep the videos coming.

[@charlesbovalis6591]

Indeed - a "GOOD" teacher is PRICELESS !!!!!!

[@ismailmatrix1]

I noticed he uses a lot of printing to explain things. That's why it seems logical. When in doubt, just print it out!

[@selehadinhabesi3855]

well said, a teacher can kill or instill in you a love for a subject

[@user-xc5xf8gp8n]

Summary: In this video, Corey taught as how to differentiate between a Class variable and instance variable, how they are related to each, other, and when each of them is more useful over the other. Class variables are variables that we set inside a class, and are shared among all instances. Corey gave a good example where the number of total employs should be the same to every employ, no matter which employee we are referring to. Therefore, emp_1.num_of_employ = emp_2.num_of_employ = Employee.num_of_employ Instance variables are variables that are different from each instance. For example, the names and the pay for each employee. They have to be different. Corey also shows that class variables and instance variables are closely related, and that class variables are kind of 'inherited' to the 'self' variables. To illustrate this, Corey shows an example of 'annual raise of pay'. He initially creates the class variable to show a case where annual raise is equal among all the employees. This variable of 1.04 was accessible through each instance, and also through the class itself(obiviously). That is, print(Employee.annual_raise) print(emp_1.annual_raise) print(emp_2.anual_rais) all printed out 1.04. However, using the .__dict___ thing, Corey shows that the intances, emp_1 and emp_2 does not contain the annual_raise value. Corey explains that if a variable is not found within an instance and programmers try to access the variable, python automatically looks in in the variable of the instance's class, and then the more classes that the instance's class inherits from. Furthermore, if we access the class variable through an instance and then change it, python creates the variable within the instance. We can check it by using the .__dict__ thing. Corey shows that annual_raise key was created when he manually changed the annual_raise value as 1.05 in the following way. emp_1.annual_raise = 1.05 however, we know that the class variable remained the same at 1.04, when printing the class variable. print(Employee.annual_raise) ==> 1.04

[@marflage]

Thank you so much. I wanted to revise everything he said but did not want to watch the entire video again. Your comment helped me with just.

[@amansinghal2431]

in the second para you said that class variables are shared among all instances but I dont think thats the case. Corey said pyhton first searches the variables in the instance but if it doesnt find it, it goes to the class of the instance and returns it from their. if you dont explicitly mention emp1.raise_amount = 1.05, emp1 instance doesnt have the raise_amount vriables. Please confirm

[@infinitedeathloop5517]

@@amansinghal2431 I think he means, when the raise_amount variable isn't found in the instances, python searches for the instance in the class and applies it to both the instances, thus making them share the same variable. I hope I was clear

[@nishantthakur5357]

Thankx a lot mate

[@aniruddhkhare2080]

@@amansinghal2431 The fact that class variables are shared among instances is correct. When class variables are used in methods using class names (as in Employee.raise_amount), then python directly accesses the class namespace, which is common for every instance. But when self is used (as in self.raise_amount), then python first searches the object's namespace, and if not found, then the class namespace. That's why Corey states that using self allows to assign different class variable values to different objects, as reassigning them (such as self.raise_amount = 1.05), makes the value a part of the object's namespace which is queried first.

[@HaroonAshrafAwan]

I enrolled into a top seller's python course on Udemy, read from some of the famous websites but I didn't find someone who teaches like you.You are, hands down, the best teacher anyone can have.

[@husainmansuri9544]

which course did you bought from udemu=y,can i know

[@michaelakingbade1036]

i made the same mistake

[@SS-lk7fs]

me too

[@ayeshavlogsfun]

Which Course did you buy .?

[@jaysphere7519]

@@ayeshavlogsfun I bought all. All of them below par compared to this.

[@charlesdeleau3086]

This is so good that I'm starting to doubt whether all his 'mistakes' are secretly ways to make us learn faster :P

[@wonderoverload0]

Who needs a Udemy course when you have Corey on KZbin. Thanks buddy for making internet useful for us.

[@engee_346]

The sleepless hours that I spent trying understand the nomenclature and the functions that he just made clear in 11 minutes... if you had an advanced professional class that cost money, I would pay for it.

[@roro4787]

I finally understand the difference between teaching and throwing information. Love your explanation Corey!

[@abdallahdataguy]

throwing information 😂😂😂

[@sandippaul468]

Underrated comment

[@nikolahuang1919]

This series is the best Python series I've ever watched. Your explanation is so clear and you just teach the right amount of useful knowledge we need.

[@coreyms]

Thanks!

[@petermaller4207]

可不是咋的！

[@sunnybeta_]

you helped me get an internship. :*

[@coreyms]

Congratulations!

[@Asterite]

@@robbyz512 for experience and understanding , thats simple even tho i wasnt in any internship :p you are basically learning how to work in that level

[@Asterite]

@@robbyz512 i think you are paid man not like alot but still

[@Asterite]

@Berke Icel oh still also a good way for experience :3

[@nomadfox9290]

@Berke Icel That's not entirely true (not being payed for internships). I actually was paid for an internship I did before I was hired on after it was over. I know for a fact the big companies like Facebook, Microsoft, Google, Twitter, etc. pay interns via an educational stipend.

[@takuz7879]

6 years later, and your videos are still helping us students. I'm in highschool and I'm literally studying for my exam through these. When I pass it'll all be because of you. THANK YOU COREY!

[@eliasvor]

did you pass?

[@takuz7879]

@@eliasvor yeah 🙌

[@derricknjoroge2494]

You have the best python OOP tutorials. Thank you, you are helping alot of people especially aspiring developers from Africa. Cheers

[@coreyms]

That's great to hear! Glad you found it helpful!

[@jeremyokuto9856]

Actually from the same country bro

[@peti826]

I know there loads of comments appreciating your work already, but man.. . I started learning python about 1,5 months ago and I have never learnt about OOP, not even its concept and the difference related to other types (still dunno them properly), yet I fully understood everything you said in both of your videos so far... Hats off dude.

[@Bartnick81]

Quality tutorial! You got my patreon backing.

[@nomoreospf]

Best Python OOP lessons for beginners!

[@thuggfrogg]

These videos are insanely good... Definitely not for a 100% noob but absolutely amazing for somebody who's hacked around and now needs a technical understanding to get to the next level. Thanks, Corey!

[@ravenjs]

I'm so so so glad that I found Corey on KZbin. His teachings are state of the art! Whenever there's something I'm confused about python, he is the first person that comes in mind. I'm so very grateful to have you as a teacher, you rock at it! Keep it up! Can't wait for more!

[@coreyms]

Thanks! Glad to have you

[@rsmrostov]

I read a ton of explanation for class attributes and instance attributes, but you explain it so clearly. Great job!

[@falconspy1668]

The best python OOP tutorial on KZbin. Thank you sir

[@gustavovzucco]

This guy is insane at teaching, thank you so much!

[@jaxwylde2139]

Wow! Learned more about classes and class variables, in the last 10 minutes, than on a full day going through online python CBT. Can't wait to watch the rest of this series.

[@elmastermaestr]

Tank you for covering all of this. I'm truly becoming better in Python because of this

[@Thurrak]

You are an outstanding teacher, showing the reasoning behind things is MASSIVELY impactful. Feels like my brain is expanding watching your videos lol

[@hectorserrano9314]

Showing the namespace was so clever to help us thoroughly understand it. Thank you so very much!

[@noamanrasul]

Oh My God. I was struggling with OOP concepts. Corey made it so simple. Corey keep on doing what you doing my good friend. Thank you.

[@vaclavvlcek4527]

Hi, I need to say your videos are really clear, comprehensive, enough detailed but not boring and too long on the other hand. I just sent you some small donate right now as appreciation. I wish I discovered your channel sooner. Thank you for all your effort!

[@SourabhDesaiBrief]

What I love about these lecture, that Errors are explained, which is more intuitive. Thanks Corey :)

[@splendorman7922]

Dude I miss your videos. Best python videos on youtube. I hope you come back and start uploading more valuable videos.

[@willylukwago6051]

I don't know why you don't have more subscribers by now, or maybe there aren't many coders out there. But I was afraid of starting learning Python until I stumbled onto this Chanel. Now I can code as a charm.

[@Soljarag5]

hands down the best OOP tutorial series... I've been using python for 2 years, but have been intimidated by Classes.... this has helped a ton!!!!!

[@harshhes]

OOPs tutorial couldn't have been more better than this.Respect from india, Mr.schafer.

[@Humon66]

COREY is just the best teacher ever!!!! Thank you COREY!!!!

[@taofeekajibade]

So, 5 years ago, this amazing video was made and I'm just seeing it in 2022! What a classic teaching it is! Thank you for the supremely brilliant delivery 👍

[@chenlily9444]

As a beginner, I was stuck with learning Python Class and so lucky to find these videos via Google search! Very informative and easy to understand. BTW, the teacher in these videos also has a nice voice ☺

[@hasanaslan2688]

Everything you explained is clear and logical. Thank you

[@TahmidulAzomSany]

You start with messing up the things, then collaborate them and make a great sense. Awesome.

[@colinsmith5972]

Corey your explanation of "Class" is just that...... CLASS. Perfect explanation!!! Total Respect.

[@IonBeamXXIV]

Thank you so much for this series, these videos are fantastic, I feel like every possible pitfall or misunderstanding one could have you articulately and expertly explain.

[@MrAverageViewer]

Corey, your videos are EXEMPLARY :) Your approach to teaching, and examples you use (e.g. Employees), have finally unlocked the hard-to-understand concepts into easier-to-understand analogies. Thank you for posting these videos!

[@ericorabello]

The best explanation on Python Classes on YT. Congrats, man

[@hashtaggamer1850]

Your pretty much the only thing and/or person who explains any of this clearly

[@Tazumm]

I've seen several sites, books, and videos that all used the Employee class as an example for OOP, however this is the only one that actually made sense and helped me understand the concepts. Thanks!

[@alessanderboy]

Hello Corey, I'd like to thank you for all the courses on Python you've made. They're way better than udemy courses and any others. You're doing a great job, captain!

[@gavravdhongadi9824]

You are literally giving me hope, appreciate it

[@unknown_f2794]

I get more explanations from your videos than what I have got from all of my courses, great work!!!!!!

[@nadik4531]

Lol your explanations are better than all my professors. How did I not find this channel years ago smh

[@sudarsandm]

Love these videos and your style of explaining complex concepts using simple examples. Thanks for your effort Corey.

[@lucdrouin2625]

Thank You Corey. You have compartmentalized key issues with easily understood practical examples. I like the logical progression of your examples.

[@madmowgli1055]

Absolutely freaking awesome. Hands down, you're providing me an A+ headstart for my bachelor course in economy informatics. Huge thumbs up for spreading absolutely logic and understandable explanations. You're amazing. Thanks.

[@cairink2110]

your videos are much better compared to many online courses and free too

[@CLacroix]

You are amazing man!!! so simple, so clean and straight forward. Every minute brings a new information

[@catalinleca6730]

Dude, you're amainzg! You're tutorials are one of the best tutorials i've ever watched! Good work!

[@charlesbovalis6591]

I have NOTHING BUT PRAISES for your style, clarity, and to the point explanation of VERY IMPORTANT concepts .... I cannot thank you enough Corey .. I will gladly contribute to your classes and start filling all the "gaps" of knowledge I need to .. You have a devoted student now :)

[@matfen7978]

Everything is so well placed and informative, thank you!

[@sudarsandm]

Going through your videos we feel like we have covered the most. What we can gain by going through multiple books you walk us through it in one video. Thank you Corey from the bottom of my heart.

[@BullNkosi]

I tried watching these videos several months ago... all went over my head. Now the lightbulbs just keep popping!!

[@starplatinumrqm]

can't express how nice and easy to understand these videos are

[@hmhamam_ham]

Thanks for making a concise and understandable lesson on 'self'. I had one semester on python and my professor could never really make it make sense and you managed to explain it is like 20 minutes. Heck yeah!

[@phamvantho4981]

Don't know how to express how grateful I am to have all these materials. Thank you a lot Corey.

[@ahnadiri]

Absolutely masterful. I rarely even need to rewind, that's how well you explain it. It's like magic.

[@simonclaeys1414]

This is so much better than my lectures and book, thank you so much!

[@anamariabalaban]

It's great that there are people with pedagogical grace, but it's really wonderful when they share their knowledge with beginners. Please don't stop what you're doing ❤

[@kareemjeiroudi1964]

What I loved about these tutorials is that he tried to cover those tricky questions such as instance namespace and class namespace ever for people that are already familiar with these concepts. Keep making videos. Your content is great!

[@harshinivbhat7817]

These are the best videos ever . I struggled to make sense of these concepts before . Now its all so damn logical and intresrting. A Million tonnes of gratitude to u !

[@vuyokazimatomela6776]

This is the best Video ever to explain classes, i have been very lost for a month trying to get this concept and you explained it in less than an hour thank you soo much. I am going to nail my computer science paper tomorrow

[@VishalMishra-hz4fy]

This is the most logical approach to class and objects, i am really glad i found you Sir! Thankyou for such a beautiful explanation. You solved every doubt!

[@davidmiricho385]

The best Python tutorials I have come across. Your explanation is just awesome. Keep up the good work.

[@Mnerd7368]

Your videos are more much effective for me to learn computer programming for my personal gain.

[@Abbekej]

You are next level, man. Respect!

[@datasciencehelp2030]

1 hour of my Grad class summed up in 11 minutes. Thank you!

[@josefh8782]

Probably the best videos Ive been able to find for beginner Python. So articulate and logical in the way you teach, it's awesome. Thanks.

[@Mak48911]

Thanks Corey, your videos are just fantastic. You put things across in a way that can be easily understood and I'm just hooked onto these videos

[@carljason4299]

On the 2nd of Feb 2020 ,this video had a 99.64% like - dislike ratio. That's insane. It stands as a testimony to the insanely great work Corey's been doing. Thank you!

[@Aseem_Bhandari]

After purchasing a few tutorial classes going through the online material this is where i got the bestsellers explanation. #Thanks Corey Schafer #Respect

[@anand29091987]

This is just pure gold. That's how any teacher should be , who makes their student eager to learn more in most simplistic way. Great work Corey.

[@yeetyeet4321]

You are highly underrated you come off as interesting and you put the rest of the videos in your description. Subscribed

[@mohamedkhodary7831]

Finding your channel is like finding a Gold mine Corey , keep up the Gold work ; - )

[@iuliapintrijal8041]

Best KZbin channel there is! Bravo!

[@owenmurray3748]

The Object-Oriented series is excellent, thanks Corey! Just wrote my first successful class in python.

[@chilinouillesdepommesdeter819]

KZbin is just like a paradise!What a great teacher!

[@JAAKAP]

BEST PYTHON OOP EXPLANATIONS I HAVE SEEN. I HAVE BOUGHT MANY ONLINE COURSES BY THEY ARE SUCKS COMPARING TO YOU.

[@humayunkabir7925]

I was thinking i am very good in OOP since got i A+(4.0) in the course both in Theory & Lab, somehow i came to the playlist & saw pretty amazing comments, so i got interest to see what's inside. i was thinking myself a pro in OOP. But the way you teach things here are amazing.

[@marcofumagalli8147]

Very Nice Corey! I have been using Python as a data science language for a couple of years and try to learn from many different source. Your videos (especially the ones on Logging) are awesome!

[@kannanv8831]

Every tiny details are explained in well manner. I am glad to get a teacher like you.

[@mrchatterjee_]

After working in the industry for 5 years, learned this concept today, just because of the way you made it. I am moving towards into a more coding technology and your videos are gold! Amazing!

[@shiggigigi]

Really? 5 years of tech support scams, and yet you don't know any basics of OOP. Now that's some top tier career dreams

[@thenode_]

Corey, to repeat the sentiment here, you really helped drive home what Object Oriented Programming almost instantly. You should have your own Coursera courses.

[@pratikkawalgikar4839]

Your videos should be at top in the youtube search for "python". I'm recommending your channel to all my friends interested in Python. Thanks Corey. You are a great teacher.

[@joeymatthews4112]

You are so thorough! I agree with others that you are a natural teacher. The pace, tone, comprehensiveness, and genuine enthusiasm are all spot-on. You are an asset! Thank you!

[@aaronmackley3472]

I've been watching several python training videos. Corey explains things more simply and more completely than anything I have watched so far. Good work.

[@coreyms]

Thanks! Glad it helped!

[@rafaelgalvan4087]

Every video is so clear thanks bro!

[@mostafanakhaei2487]

Amazing Teacher. How easily you explained the concepts supprised me. WOW!

[@MG-pw7jp]

Thank you Soo much for these videos Corey. Your videos are a life saver. I literally didn't pay much attention in class because they were soo stretched and boring but after seeing your videos I feel like a class genius.

[@sudarsandm]

Awesome explanation.

[@aditimore3967]

You might have no idea how helpful this was to us.

[@MrKatdar]

Corey, you must be the best instructor in this universe. I love watching your videos. Thank you

[@arenlegit7047]

i love you.i learn more by watching these vids then i do at my uni lectures honestly. you're such a great help

[@stevenshelby2675]

This is the type of youtuber whom I would gladly watch 10 straight ads on their video

[@Finn-jp6pn]

You, sentdex, Traversy Media are the teachers we all need in Uni but don't have. The day I get a job, I'll definitely support you. Thank you for sharing your knowledge.

[@kairu9373]

first 4 minutes of the video and it already caught my attention. This is very interesting for me to visualize how everything works with Classes and you've done it perfectly! Thank you!

[@daegudude1048]

Why are you such a good teacher?