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Figure 4 shows the output produced by the code in Listing 5 .

Figure 4 . Output from the code in Listing 5.
Available stations in Dallas {98.3: 'KNON', 98.7: 'KLUV', 91.7: 'KKXT', 97.9: 'KBFB'}Program the buttons Play the three programmed stationsPlaying KNON Playing KBFBPlaying KKXT

The class named Radio

The definition of the class named Radio begins in Listing 6 . The first line of code in a class definition consists of the keyword classfollowed by the name of the class. This is followed by the name of another class in parentheses, which I will explain in a future module on class inheritance . As is common in Python, the closing parenthesis is followed by a colon (:)character. The colon is followed by the indented class body.

Listing 6 . Beginning of the class named Radio.
class Radio(object): #This class provides the plans from which the radio objects are built.stations = {"Austin":{91.7:"KVRX",95.5:"KKMJ",98.1:"KVET",93.7:"KLBJ"}, "Dallas":{98.3:"KNON",91.7:"KKXT",97.9:"KBFB",98.7:"KLUV"}}

A class variable named stations

The class body in Listing 6 begins with a variable named stations that references a dictionary object. The dictionary object contains twonested dictionary objects. One of the nested objects provides information about radio stations in Austin. The other nested object provides informationabout radio stations in Dallas. This is the source of the radio call sign information for Austin and Dallas shown in Figure 3 and Figure 4 .

IMPORTANT: According to The Python Tutorial -- Class and Instance Variables , the variable named stations is a class variable that is shared by all instances (objects) of the class. I will have more to say about class variables and instance variables in a future module.

The __init__ method

As I mentioned earlier, when a function is defined inside of a class definition, it is called a method. Listing 7 defines a special method named __init__ . (Note that two underscore characters are required on each side of the word init .)

Listing 7 . The __init__ method.
def __init__(self): self.stationNumber = [0,0,0]

According to The Python Tutorial -- Class Objects ,

"When a class defines an __init__() method, class instantiation automatically invokes __init__() for the newly-created class instance."

Thus, the __init__ method can be used to initialize various aspects of a new object when it is instantiated. (This is roughly analogous to the constructor in other OO languages.)

The code inside the __init__ method in Listing 7 creates a new variable named stationNumber and initializes it to refer to a three-element list.

According to The Python Tutorial -- Class and Instance Variables , variables that are created in this manner (inside class methods) are called instance variables and are "for data unique to each instance (object)."

Therefore, the variable named stations from Listing 6 is shared among radio01 and radio02 in Listing 9 . However, radio01 and radio02 each has its own copy of the variable named stationNumber from Listing 7 and those variables are not shared among objects.

Questions & Answers

Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
hi
Loga
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
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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
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