Python OOP Tutorial 2: Class Variables
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- čas přidán 26. 07. 2024
- 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...
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Your videos are more informative than my university lectures
Thanks a lot! That's a nice compliment. I'm glad to hear you find them useful.
and short and arent booooooring
This is so true. We obtain more information on those really short videos than we do in those long lectures on universities.
True Story of every university
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.
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.
Indeed - a "GOOD" teacher is PRICELESS !!!!!!
I noticed he uses a lot of printing to explain things. That's why it seems logical. When in doubt, just print it out!
well said, a teacher can kill or instill in you a love for a subject
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
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.
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
@@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
Thankx a lot mate
@@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.
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which course did you bought from udemu=y,can i know
i made the same mistake
me too
Which Course did you buy .?
@@ayeshavlogsfun I bought all. All of them below par compared to this.
This is so good that I'm starting to doubt whether all his 'mistakes' are secretly ways to make us learn faster :P
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Thanks buddy for making internet useful for us.
I finally understand the difference between teaching and throwing information. Love your explanation Corey!
throwing information 😂😂😂
Underrated comment
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.
Thanks!
可不是咋的！
You have the best python OOP tutorials. Thank you, you are helping alot of people especially aspiring developers from
Africa. Cheers
That's great to hear! Glad you found it helpful!
Actually from the same country bro
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!
did you pass?
@@eliasvor yeah 🙌
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.
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Thanks! Glad to have you
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What a classic teaching it is!
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Congratulations!
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@Berke Icel oh still also a good way for experience :3
@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.
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What I love about these lecture, that Errors are explained, which is more intuitive.
Thanks Corey :)
Best Python OOP lessons for beginners!
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 ☺
I read a ton of explanation for class attributes and instance attributes, but you explain it so clearly. Great job!
Showing the namespace was so clever to help us thoroughly understand it. Thank you so very much!
As a CS person myself, I’ve seen numerous tutorial videos. Yours is the most logical, right to the point, and easy to understand. 👍 Hope you’ll create more contents.
Corey your explanation of "Class" is just that...... CLASS. Perfect explanation!!! Total Respect.
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!
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!
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I always had difficulties understanding Python class well, until I found this video that makes it so intuitive.
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Thanks! Glad it helped!
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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.
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Finding your channel is like finding a Gold mine Corey , keep up the Gold work ; - )
BEST PYTHON OOP EXPLANATIONS I HAVE SEEN.
I HAVE BOUGHT MANY ONLINE COURSES BY THEY ARE SUCKS COMPARING TO YOU.
I first started watching these videos to help my son, who is currently taking coding courses. I found your videos very very helpful. Thanks a lot, Corey..
I have been searching for good tutorials on Python for years, and this series is by far is the most informative. Thank you!
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
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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!
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.
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Senior here and taking a different online course just to keep the synapses working. Well, you have it way over them in teaching quality. Wish I had seen you first. Thank you.
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!
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You might have no idea how helpful this was to us.
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The best explanation on Python Classes on YT. Congrats, man
1 hour of my Grad class summed up in 11 minutes. Thank you!
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.
Posted 4 years back but still, I did not find any other tutorial as clear as these classes one. I have just started learning python and I really appreciate you making these videos. You are an awesome teacher.
Being from a non-technical background, I was struggling to understand the OOP. But now the concept is clear to me. Thank You..
Dude, these tutorials are mindblowing.. I've gone through a few OOP classes and never really understood the concept so i can write my own things with it, after watching tutorial 1 and 2 i now have a very good understanding how to rewrite a whole script i got. Thanks, i never sub but this deserves a sub.
Glad it helped!
Who gives dislikes for gems like these??? For now I only have love and respect for you Corey, Patreon to follow soon :)
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All these comments are spot on. I just came from another very popular python instructor on youtube and he skipped over the fact python going to the class attribute if it doesn't find it on the instance of the class. Might be in the paid tutorial he says you can buy if you want to learn more lol!
Everything is so well placed and informative, thank you!
You are literally giving me hope, appreciate it
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Bow down to the maestro...the way you teach is still the best after 5 years of this video...I have been to lots of tutorials for python but always missing the concept...you made it like a butter in the frying pan...it just slips through your mind and I feel satisfied after learning from your videos.... please don't stop your videos...the world needs teacher like you ... #respect
Corey, to repeat the sentiment here, you really helped drive home what Object Oriented Programming almost instantly. You should have your own Coursera courses.
You are next level, man. Respect!
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.
I could cry. I wrote a program that needed to automaticly create Buttons and I sat down there for like 5 hours to do this but now I can easily make the same program in 5 minutes and a third of the code. Thank you so much!!
Every video is so clear thanks bro!
I've been using Sololearn, but this is more straightforward and easy to understand. Thanks!
I am using Sololearn as well and Corey is way better at the OPP stuff!
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You helped me finally understand object oriented programming in just one video after hours of surfing the web without any result.