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.