Object Oriented Programming With Python (part 1) (
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As a true object-oriented language, Python is a great place to
start learning about OO programming. In this first segment of a two-part
article, take your Python skills to the next level with a discussion of
classes and class instances. Practical (and not-so-practical) examples
included.You're probably tired of hearing me say it, but indulge me one more time - when
it comes to object-oriented programming, very few languages have Python's
capabilities.
This is primarily because Python was built from the ground
up as an object-oriented language, and so provides built-in constructs that make
it simple for developers to structure code for maximum reusability. Python's
"dynamic typing", which automatically recognizes objects like numbers, strings
and lists, and negates the need to declare variable types and sizes, offers an
advantage not found in languages like C or Java, while automatic memory
allocation and management, together with a vast array of pluggable libraries and
high-level abstractions, complete the picture.
Over the course of this
two-part article, I'm going to take an in-depth look at Python's OO
capabilities, together with examples and explanations to demonstrate just how
powerful it really is. I'll be covering most of the basics - classes, objects,
attributes and methods - and a couple of the advanced concepts - constructors,
destructors and inheritance. And if you're new to object-oriented programming,
or just apprehensive about what lies ahead, don't worry - I promise this will be
a lot easier than you think.
Let's get going!{mospagebreak title=The
Basics} Before we begin, let's just go over the basics quickly:
In
Python, a "class" is simply a set of program statements which perform a specific
task. A typical class definition contains both variables and functions, and
serves as the template from which to spawn specific instances of that
class.
These specific instances of a class are referred to as "objects".
Every object has certain characteristics, or "properties", and certain
pre-defined functions, or "methods". These properties and methods of the object
correspond directly with the variables and functions within the class
definition.
Once a class has been defined, Python allows you to spawn as
many instances of the class as you like. Each of these instances is a completely
independent object, with its own properties and methods, and can thus be
manipulated independently of other objects. This comes in handy in situations
where you need to spawn more than one instance of an object - for example, two
simultaneous database links for two simultaneous queries, or two shopping
carts.
Classes also help you keep your code modular - you can define a
class in a separate file, and include that file only in the pages where you plan
to use the class - and simplify code changes, since you only need to edit a
single file to add new functionality to all your spawned objects.
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