Can anybody explain concepts of OOP and correct this code

Question

So i am writing this very simple encryptor and decryptor in python.I understand it procedural way but i want to make a class of it. Here is the code

class Encrypt():
    def __init__(self,scentence):
            self.scentence = scentence



    def encryptor(self):
            result = []
            for letter in self.scentence:
                    l = ord(letter)+20
                    result.append(l)
            for numbers in result:
                    print(numbers,end = '')
                    print(" " , end = '')
            print(result)
    def decryptor(result):
            print(result)

            end_string = ""
            for j in result:
                    l = int(j)
                    l = l-20
                    l = chr(l)
                    end_string = end_string + l


            print("The decrypted message is below:")
            print(end_string)

f = Encrypt("helloe")
f.encryptor()
f.decryptor()

So when i run this code there is error as follows

for j in result: TypeError: 'Encrypt' object is not iterable

It would be very helpful for someone to explain the concept of SELF and OBJECT and CLASS

Answer 1

In Python, the first parameter for class methods is always self (whereas in other object-oriented languages like C++ and Java this parameter is implicit). For an explanation of why, see https://stackoverflow.com/a/2709832/4454124 . ( self is merely the conventional name given to the first parameter, but the name could be anything, like self , this , banana , or result )

Because you don't have the self parameter in your decryptor() method, the Python interpreter will try to interpret the parameter you do provide ( result ) as the self parameter, meaning it expects it to be of type Encrypt which it is not, hence the error.

As a side note, in an object-oriented program the name of the class should be a noun, and method names should be verbs -- so in your program you would have a class called "Encryptor" and methods called "encrypt" and "decrypt".