<< Chapter < Page Chapter >> Page >
Listing 4 . Object can modify itself at runtime.
class TestClass(object): def addInstanceVar(self,data):self.iVar = data

I am presenting and explaining this program for a couple of different reasons:

  • It will be useful in explaining the method named __init__ in the next program in this module.
  • It will be useful in explaining issues surrounding class variables in a future module.

Add an instance variable to one object and display it

The other difference between the two programs is shown in Listing 5 . Instead of accessing the object directly to add the new instance variable, as was done in Listing 2 , the code in Listing 5 calls the method named addInstanceVar on the object to cause the new instance variable to be added.

Listing 5 . Add an instance variable to one object and display it.
print("Add an instance variable to one object and display it") ref01.addInstanceVar(1234)print(ref01.iVar)

As mentioned earlier, the end result is the same as you will see if you examine the output from the program shown in Listing 11 .

Visualize the code in Listing 10

Once again, I recommend that you create a visualization for the code in Listing 10 and step through the program one instruction at a time. As you do that, pay attention tothe movements of the red and green arrows on the left, the diagram on the right, and the printed material at the bottom. That should help you to betterunderstand how a Python object can modify itself at runtime.

The method named __init__

You learned in the previous program that a method belonging to an object can add an instance variable to an object at runtime.

You also learned in an earlier module that if your class contains a method named __init__ , that method will be executed automatically in conjunction with the instantiation of the object. As I understand it, that isprobably the last thing that happens before the new object's reference is returned to be saved for later use.

A complete listing of a program that I will use to discuss the __init__ method is shown in Listing 11 . The output produced by that program is shown in Figure 7 . As usual, I will explain the program in fragments.

A class with an __init__ method

Listing 6 shows the definition of a class named TestClass that contains a method named __init__ in addition to a method named addInstanceVar as in the previous program.

Listing 6 . A class with an __init__ method.
class TestClass(object): def __init__(self,data):self.iVar01 = datadef addInstanceVar(self,data): self.iVar02 = data

When either of the methods shown in Listing 6 are executed, a new instance variable will be added to the object and initialized with an incoming datavalue. Since the method named __init__ is always executed automatically in conjunction with the instantiation of an object, the initial state of theobject will include an instance variable named iVar01 .

Instantiate and display two objects

The code in Listing 7 instantiates and prints two new objects of the class named TestClass . You can view the output produced by the code in Listing 7 in Figure 7 . There probably won't be any surprises there.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
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
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
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
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
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
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!





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