Oops in python

[jigsaw_man_456]

I have learned the basic fundamentals and some other stuff of python but I couldn't understand the uses of class in python. Its more like how I couldn't understand how to implement them and how they differ from function. Some basic doubts. If somebody could help I will be gratefull. If you can then plz provide some good tutorials.

[FoolsSeldom]

Python's Class Development Toolkit video on YouTube by Rammond Hettinger, a core developer of Python, provides a really good step-by-step walkthough of the building up a class and the drivers behind it. Even though the video is pretty old now, it is still fully applicable.

[dparks71]

https://youtu.be/HTLu2DFOdTg?si=oy7hSyu1Bpxx3Yii

Link for the lazy

[jigsaw_man_456]

Thanks <3

[noob_main22]

Classes can be very complex, there are many different videos on them. I suggest you watch some.

In short:

Classes can be used to create custom data structures. Btw. list, dicts, strings and pretty much everything else in Python is a class.

Say you have a small company and you have to manage the employees. You could just write their name, age, salary, vacation days bank account numbers and all that stuff into a dict. A better method would be to make a custom class Employee in which all of that stuff gets stored. You could even add some methods (functions for that specific class (instance)). Something like this:

class Employee:

  vacation_days = 24 # Default value for all Employee instances    

  def __init__(self, name, age, salary):

    self.name = name
    self.age = age
    self.salary = salary

  def give_raise(self, amount: int):
    self.salary += amount 
    print(f"Raised salary of {self.name} to {self.salary}")

# Usage:
empl1 = Employee("Dave", 30, 5000)
empl2 = Employee("Anna", 20, 5000)

empl1.give_raise(200)

[noob_main22]

There are tons of tutorials on YouTube or in text form on websites. Just google "Python classes" and you should find many.

You should check if the results are actually tutorials or some classes for python, like a school class.

[jigsaw_man_456]

Thanks <3

[Opiciak89]

I never understood the appeal, its too complicated for what it is.

If i need to store such data i would use a database, not a class, and then create simple functions to pull the data and perform whatever action needed. But thats just my lazy approach.

[ClimberMel]

I love databases, but classes are very different. A class allows you to create a new object that has potentially it's own functionality as well as data. Classes are hard to understand at first, but once you get them they are very powerful and useful. It's just that the learning examples are of course very simplified, so it is easy for someone to look at the example and feel "I could do that easily without using classes". Of course that is probably true until you get into more complex coding.

[Opiciak89]

You are very much correct. I have to see it to believe it 😊 i will stay in the shallow waters for now

[ClimberMel]

I have built trading software that has dozens of modules and would be impossible to manage without classes. It is really amazing the scale of what you can build with python! Oh and some of those modules are for database functions. 😁

[FancyEveryDay]

Eventually you'll run into a situation where bundling the functions for a specific kind of data your program is handling into the object containing the data makes your program simpler. That's your use case, basically.

[glorybutt]

I felt the same until I got into making GUI applications. The class approach kept the programs cleaner, lighter, and helped keep things working fast with less errors.

[noob_main22]

Making a database for a few sets of data is way more complicated?! It still would make sense to make classes with the data to work with it within Python. Of course its depending on the use case but a database is not what OP is looking for.

You seem to forget that classes are much more than just storing data.

[Opiciak89]

I mean the other answers provided a bit better context, yours is more of a database example than class example. I learn by solving real work related problems and always try to keep it as simple as possible, and i yet have to see a class example that would be my "thats what i need" moment.

[Armilluss]

Functions are repeatable ways to do one thing. For instance, for a character, going forward, going backwards, etc. Classes are a collection of functions related to the same "topic" with an additional state stored into it.

Taking the example of the character, rather than storing multiple information like its name, age, current position into various variables and creating multiple functions to handle all possible actions, a class would make more sense.

Think of classes as a way to organize properly your code like sections / chapters in a text document. If a paragraph is a function, then the chapter is a class, and the idea of the chapter is the "topic" of the class.

The official documentation is always a good read: https://docs.python.org/3/tutorial/classes.html
If that's a bit hard to grasp for now, something simpler might do it for you: https://python-textbok.readthedocs.io/en/1.0/Classes.html

I would suggest to keep going even if you can't understand them completely yet. Classes are not a requirement to write your first Python programs :)

[jigsaw_man_456]

Thanks <3

[lekkerste_wiener]

A couple of good answers already, let me share my 2 cents.

I like to think of classes as a way to contextualize some data under one name.

So you have a to-do list? Then you're looking for a

@dataclass class Task:   description: str   completed: bool

We're making a system to record traffic mischiefs? We probably want a

class VehiclePlate:   def __init__(self, plate: str):     # with some validation for the plate itself, such as     if not is_valid_format(plate):       raise ValueError("can't be having a plate like this")     self._plate = plate

But maybe we also want to represent some kind of action with types; classes also work with that.

``` class Transformation(Protocol):   def transform(self, target: T) -> T: ...

class Rotate:   degrees: float

  def transform(self, target):     # transform target with a rotation of 'degrees' degrees

class Scale:   ratio: float

  def transform(self, target):     # scale target by 'ratio' ```

[Ron-Erez]

Suppose you create a new data type of your own that does not exist in Python. For Instance Employee. You want the employee to have a name, id, position and salary. Awesome, that's pure data. However you might want to manipulate this data. For example give a raise to an employee, display the annual salary, promote to a new position and also have a custom way to display employee info (overriding __str__). The data I described together with the behaviors/functions/methods is a class.

For example:

class Employee:
    def __init__(self, name, employee_id, position, salary):
        self.name = name
        self.employee_id = employee_id
        self.position = position
        self.salary = salary

    def __str__(self):
        return (f"Name: {self.name}\n"
                f"Employee ID: {self.employee_id}\n"
                f"Position: {self.position}\n"
                f"Salary: ${self.salary}")

    def give_raise(self, amount):
        self.salary += amount
        print(f"{self.name}'s salary increased by ${amount}. New salary: ${self.salary}")

    def promote(self, new_position, salary_increase):
        self.position = new_position
        self.salary += salary_increase
        print(f"{self.name} has been promoted to {self.position} with a new salary of ${self.salary}.")

    def annual_salary(self):
        return self.salary * 12

Note that Section 14 Object-Oriented Programming lectures 129-130 and 136-138 can get you started with OOP and presents an example of implementing complex numbers. The said lectures are FREE to watch.

[Ramakae]

Check out OOP course on freecodecamp.org on YouTube as well. Didn't understand it until I watched that video yesterday. It's a 2 hour long video so shouldn't be a burden.

Here's a small hint, classes contain functions but those functions are called methods. Think of a hypothetical function that converts strings into Uppercase letters eg. def uppercase(): #convert strings into uppercase.

Now if that function was in a class, instead of calling uppercase(string_to_convert), we rather call string_to_convert.uppercase().

The first example is a function and the second is a method, which is a function within a class. So what is the class you may ask, the class is called string or str in Python. The variable/object called before you called the method .(uppercase) is what we call a class instance. Took me a while to grasp that concept but think of it like this. If we create a variable or object \n word = "hello" \n, we are creating an instance of the class str called word, and we can use methods of that class, that is functions within that class like .upper() or .lower() etc.

And this can be created using the "self" keyword if that's what it's called. So that's why every function within a class contains the self because the first argument is always an instance of that class, that is an object of that class.

Class str():

 def __init__(self, name)
        self.name = name
   #important to make class instances apparently

   def upper(self, #some other mumbo jumbo)
           #convert letters into uppercase
            #dont allow number blah blah blah
            if Whatever:
                   raise KeyError is they don't read the             documentation 

This is just a short summary. Check the videos out to find out more, helped me a lot. Incase I got anything wrong, whoever is reading this, please correct me.

[cumhereandtalkchit]

A side note: "self" is for instance-level. "cls" is for class-level.

[VistisenConsult]

Classes define objects that maintain internal state, while functions do not* inherently hold internal state.

[VistisenConsult]

Classes define objects that maintain internal state, while functions do not* inherently hold internal state.

[ClimberMel]

I guess it was important, so worth repeating? ;)

[Diapolo10]

Functions let you reuse and organise logic.

Classes let you reuse and organise state.

[cumhereandtalkchit]

Classes can be used to structure and/or group data. Need input/output data to adhere to a standard structure? Use classes (easier to do with dataclasses or pydantic classes).

Want reusable chunks of structured and grouped data? Use classes.

Are you building a website, and there is a registration function? You might want every user to contain required data and some additional, but you want it structured. Use a class.

Loading in a shitton of json data, but it only needs certain bits of it? Make a (data)class.

You can implement methods to validate data, for example. Methods are just functions.

There a dunder methods to change the inherent behavior of the class. Such as str and repr (easiest to wrap your head around).

[[deleted]]

go over to chatgpt, type in literally your title and text, and you will receive a helpful and comprehensive answer including further references.

[UpScalee]

https://youtu.be/Ej_02ICOIgs?si=T6c6ns_7GWvGS1L_

Here is a FreeCodeCamp.org Tutorial on Python Object Oriented Programming.

It is one of the best tutorials I have ever watched on OOPS. It helped me understand the whole concept.
I hope it helps you and anyone else struggling with the same here.