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If both the object and the class contain attributes with the same name, the attribute in the object will shadow or hide the attribute in the class. I willdemonstrate the impact of this later.

If the search pattern described above is correct, we would expect the code in Listing 5 to display the values contained in each of the two new class variables belonging to the class named TestClass . Figure 2 shows the output produced by the code in Listing 5 and verifies that the search pattern described above is probably correct. The values stored in the new class variables are displayedin Figure 2 by the code in Listing 5 .

Figure 2 . Output of the code in Listing 5.
Display both class variables via one object ref01: ABCDref01: 1234

Display both class variables via the other object

The code in Listing 6 along with the output shown in Figure 10 shows unsurprisingly that the other object that was instantiated from TestClass can be used to access and display the same contents of the same two class variables.

Listing 6 . Display both class variables via the other object.
print("Display both class variables via the other object") print("ref02: " + ref02.classVar01)print("ref02: " + ref02.classVar02)

This is because class variables belonging to a class are shared among all objects instantiated from that class unless shadowed by an instance variablehaving the same name in an object of the class. This will be demonstrated in the programs that follow.

Typical class variable usage

Listing 16 shows a program that probably comes closer to the intended use of class variables than the code in the earlier program shown in Listing 15 . The output from the code shown in Listing 16 is shown in Figure 11 .

This program demonstrates that class variables are shared among the objects instantiated from a class. It also demonstrates that changes to class variablesin that class impact all of the objects instantiated from the class.

The class definition

Listing 7 shows the definition of the class for this program including the creation andinitialization a class variable named classVar . The class definition also includes a couple of methods that I will discuss later.

Listing 7 . The class definition.
class TestClass(object): classVar = [1,2,3,4]def modifyClassVar01(self): self.classVar.append("a")def printClassVar01(self): print(str(self)[10:40]+ ": " + str(self.classVar)) print("1 Display class var using class: " + str(TestClass.classVar))

Listing 7 also contains a print statement that prints the value of the variable named classVar by using the name of the class, TestClass , to access the variable. The output is shown in Figure 3 .

The output shown in Figure 3 faithfully reproduces the initial value of the class variable shown in the second line of text in Listing 7 .

Figure 3 . Output from the code in Listing 7.
1 Display class var using class: [1, 2, 3, 4]

Instantiate two objects from the class

Listing 8 instantiates two separate and distinct objects from the class named TestClass . Those objects' references are stored in the variables named ref01 and ref02 .

Questions & Answers

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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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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