<< Chapter < Page Chapter >> Page >

A python class definition is a set of plans

The same is true for software objects. In order to create a software object in Python, it is necessary for someone to first create a plan.In Python, we refer to that plan as a class . The class is defined by a Python programmer. Once the class definition is available, that programmer (or other programmers) , can use it to produce large numbers of nearly identical objects.

An instance of a class

If we were standing at the output end of the factory that produces car radios, we might pick up a new radio and say that it is an instance of the plans used to produce the radio. (Unless they were object-oriented programmers, the people around us might think we were a little odd when they hear us say that.) However, it is common jargon to refer to a software object as an instance of a class.

To instantiate an object

Furthermore, somewhere along the way, someone turned the word instance into a verb, and it is also common jargon to say that when creating a new object, we are instantiating an object.

Program code

As mentioned above, I will explain a program that uses the analogy of a car radio to illustrate several aspects of Python classes and objects.

I will explain this program in fragments. A complete listing of the program is provided in Listing 9 near the end of the module. The output from running the program is shown in Figure 6 . Because this is an overview module, this explanation will gloss over various details. I willrevisit and explain many of those details in future modules.

Manufacture a three-button radio

As you will see if you examine Listing 9 , this program defines a class named Radio . That class can be used to create objects that simulate car radios havingthree station-selector buttons and a scan button. I will explain that class later. First I will explain how to use the class.

Listing 1 shows the code necessary to create (instantiate) a single instance of the Radio class and to store that object's reference in a variable named radio01 . (In OOP jargon we say that an object is an instance of a class.) This simulates the manufacturing of the radio and the installation of the radio in a car.

Listing 1 . Manufacture a three-button radio.
#Manufacture a 3-button radio radio01 = Radio()

As a practical matter, the code required to instantiate a Python object looks just like the code required to call a function having the same name asthe class from which the object is being instantiated. In my opinion, this causes Python to be a little less readable than Java, which uses a specialsyntax to create an object.

Scan for available stations

Next we want to program the station-selector buttons to cause our favorite radio stations to be played when we press a button. First, however, we willsimulate pressing the scan button on the radio to learn about the stations that are available in the area.

Listing 2 uses the reference variable named radio01 to call a method named scan belonging to the object referred to by radio01 . As you will see later when we examine the class definition, the scan method requires the name of the city as an incoming parameter and returns a reference to a dictionary that relatesfrequencies to radio station call signs in that city. The returned reference is stored in the variable named radio01Stations .

Questions & Answers

the diagram of the digestive system
Assiatu Reply
How does twins formed
William Reply
They formed in two ways first when one sperm and one egg are splited by mitosis or two sperm and two eggs join together
Oluwatobi
what is genetics
Josephine Reply
Genetics is the study of heredity
Misack
how does twins formed?
Misack
What is manual
Hassan Reply
discuss biological phenomenon and provide pieces of evidence to show that it was responsible for the formation of eukaryotic organelles
Joseph Reply
what is biology
Yousuf Reply
the study of living organisms and their interactions with one another and their environments
AI-Robot
the study of living organisms and their interactions with one another and their environment.
Wine
discuss the biological phenomenon and provide pieces of evidence to show that it was responsible for the formation of eukaryotic organelles in an essay form
Joseph Reply
what is the blood cells
Shaker Reply
list any five characteristics of the blood cells
Shaker
lack electricity and its more savely than electronic microscope because its naturally by using of light
Abdullahi Reply
advantage of electronic microscope is easily and clearly while disadvantage is dangerous because its electronic. advantage of light microscope is savely and naturally by sun while disadvantage is not easily,means its not sharp and not clear
Abdullahi
cell theory state that every organisms composed of one or more cell,cell is the basic unit of life
Abdullahi
is like gone fail us
DENG
cells is the basic structure and functions of all living things
Ramadan
What is classification
ISCONT Reply
is organisms that are similar into groups called tara
Yamosa
in what situation (s) would be the use of a scanning electron microscope be ideal and why?
Kenna Reply
A scanning electron microscope (SEM) is ideal for situations requiring high-resolution imaging of surfaces. It is commonly used in materials science, biology, and geology to examine the topography and composition of samples at a nanoscale level. SEM is particularly useful for studying fine details,
Hilary
cell is the building block of life.
Condoleezza Reply
what is cell divisoin?
Aron Reply
Diversity of living thing
ISCONT
what is cell division
Aron Reply
Cell division is the process by which a single cell divides into two or more daughter cells. It is a fundamental process in all living organisms and is essential for growth, development, and reproduction. Cell division can occur through either mitosis or meiosis.
AI-Robot
What is life?
Allison Reply
life is defined as any system capable of performing functions such as eating, metabolizing,excreting,breathing,moving,Growing,reproducing,and responding to external stimuli.
Mohamed
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Itse 1359 introduction to scripting languages: python. OpenStax CNX. Jan 22, 2016 Download for free at https://legacy.cnx.org/content/col11713/1.32
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Itse 1359 introduction to scripting languages: python' conversation and receive update notifications?

Ask