General programming question. When to use OOP?

Question

My program needs to do 2 things.

1. Extract stuff from a webpage.

2. Do stuff with a webpage.

However, there are many webpages, such as Twitter and Facebook.

should I do this?

def facebookExtract():
    code here
def twitterExtract():
    code here
def myspaceExtract():
    code here
def facebookProcess():
    code here
def twitterProcess():
    code here
def myspaceProcess():
    code here

Or, should I have some sort of class? When is it recommended to use classes, and when is it recommend to just use functions?

Answer 1

"My program needs to do 2 things."

When you start out like that, the objects cannot be seen. You're perspective isn't right.

Change your thinking.

"My program works with stuff"

That's OO thinking. What "stuff" does your program work with? Define the stuff. Those are your basic classes. There's a class for each kind of stuff.

"My program gets the stuff from various sources"

There's a class for each source.

"My program displays the stuff"

This is usually a combination of accessor methods of the stuff plus some "reporting" classes that gather parts of the stuff to display it.

When you start out defining the "stuff" not the "do", you're doing OO programming. OO applies to everything, since every single program involves "doing" and "stuff". You can chose the "doing" POV (which is can be procedural or functional), or you can chose the "stuff" POV (which is object-oriented.)

Answer 2

My favorite rule of thumb: if you're in doubt (unspoken assumption: "and you're a reasonable person rather than a fanatic";-), make and use some classes. I've often found myself refactoring code originally written as simple functions into classes -- for example, any time the simple functions' best way to communicating with each others is with globals, that's a code smell, a strong hint that the system's factoring is not really good -- and often refactoring the OOP way is a reasonable fix for that.

Python is multi-paradigm, but its central paradigm is OOP (much like, say, C++). When a procedural or functional approach (maybe through generators &c) is optimal for some part of the system, that generally stands out -- for example, static functions are also a code smell, and if your classes have any substantial amount of those THAT is a hint to refactor things to avoid that requirement.

So, assuming you have a rich grasp of all the paradigms Python affords -- if you're STILL in doubt, that suggests you probably want to go OOP for that part of your system! Just because Python supports OOP even more wholly than it supports functional programming and the like.

From your very skeletal code, it seems to me that each extract/process pair belongs together and probably needs to communicate state, so a small set of classes with extraction and processing methods seems a natural fit.