Python OOP Tutorial 2: Class Variables
ฝัง
- เผยแพร่เมื่อ 16 ก.ค. 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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#Python
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.
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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
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.
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
Who needs a Udemy course when you have Corey on TH-cam.
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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.
I finally understand the difference between teaching and throwing information. Love your explanation Corey!
throwing information 😂😂😂
Underrated comment
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.
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!
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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?
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Africa. Cheers
That's great to hear! Glad you found it helpful!
Actually from the same country bro
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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Congratulations!
@@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
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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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Best Python OOP lessons for beginners!
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Thanks! Glad to have you
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.
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What I love about these lecture, that Errors are explained, which is more intuitive.
Thanks Corey :)
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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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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!
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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!
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.
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Thanks! Glad it helped!
Being from a non-technical background, I was struggling to understand the OOP. But now the concept is clear to me. Thank You..
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.
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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!
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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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BEST PYTHON OOP EXPLANATIONS I HAVE SEEN.
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As somebody who used C# for years, and is now picking up some python. Thank you for clearing up some of what I saw as weirdness with the way python does things. Its all clear now and simple.
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Corey, to repeat the sentiment here, you really helped drive home what Object Oriented Programming almost instantly. You should have your own Coursera courses.
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Awesome explanation.
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To me classes have been the hardest part of Python to learn - but from what I've watched so far, I think I kind of get the idea. Thank You!
The Object-Oriented series is excellent, thanks Corey! Just wrote my first successful class in python.
Who gives dislikes for gems like these??? For now I only have love and respect for you Corey, Patreon to follow soon :)
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!
Mind blown..!!! 20+ years ago I was working with Macromedia (Macromind) Director and as a visual designer without coding knowledge or experience I struggled to master Lingo. Over time I ended up at the level of an OOP Lingo coder, albeit one relying heavily on copied code segments and fiercely treasure code examples that I'd gotten to work. FF 20 years and I've returned to coding in the form of Python.
SUDDENLY with your videos a window has opened on the murky interior I previously inhabited. I now understand the concepts that you are talking about rather than piecing together code samples. ALL of your videos that I have worked through have been enlightening, fun and edifying. Thank you so much for giving all of this.
Corey, you must be the best instructor in this universe. I love watching your videos. Thank you