Object Orientation Overview¶

In the Beginning there was the GOTO.

And in fact, there wasn’t even that.

Programming Paradigms¶

https://en.wikipedia.org/wiki/Programming_paradigm

Software Design¶

Good software design is about code re-use, clean separation of concerns, refactorability, testability, etc...

OO can help with all that, but:

It doesn’t guarantee it
It can get in the way

What is Object Oriented Programming?

“Objects can be thought of as wrapping their data within a set of functions designed to ensure that the data are used appropriately, and to assist in that use”

http://en.wikipedia.org/wiki/Object-oriented_programming

Even simpler:

“Objects are data and the functions that act on them in one place.”

This is the core of “encapsulation”

The Dominant Model¶

OO is the dominant model for the past couple decades, but it is not the only model, and languages such as Python increasingly mix and blend among models.

Object Oriented Concepts¶

Classes

Instances or Objects

Encapsulation

Class and instance attributes

Subclassing

Overriding methods

Operator Overloading

Polymorphism

Dynamic Dispatch

Definitions¶

class: A category of objects: particular data and behavior: A “circle” (same as a type in python)
instance: A particular object of a class: a specific circle
object: The general case of an instance – really any value (in Python anyway)
attribute: Something that belongs to an object (or class): generally thought of as a variable, or single object, as opposed to a ...
method: A function that belongs to a class

Python and OO¶

Is Python a “True” Object-Oriented Language?

What are its strengths and weaknesses vis-a-vis OO?

It does not support full encapsulation, i.e., it does not require classes, etc.

Folks can’t even agree on what OO “really” means

See: The Quarks of Object-Oriented Development

Deborah J. Armstrong

http://agp.hx0.ru/oop/quarks.pdf

Think in terms of what makes sense for your project: – not any one paradigm of software design.

OO Buzzwords

data abstraction

encapsulation

modularity

polymorphism

inheritance

Python provides for all of this, though it doesn’t enforce or require any of it.

Python’s roots¶

C
C with Classes (aka C++)
Modula2

You can do OO in C¶

Which today is not considered an OO Language.

See the GTK+ project.

OO languages give you some handy tools to make it easier (and safer):

polymorphism (duck typing gives you this)

inheritance

You will need to understand OO¶

It’s a good idea for a lot of problems
You’ll need to work with OO packages

(Much of the standard library is object oriented)