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Figure 3. The truth about pigeonholes.

missing image

A code visualizer tool

The image in Figure 3 was produced using a code visualizer tool from the Online Python Tutor . At this point in the course, you can ignore the buttons at the bottom of Figure 3 and concentrate on the code window on the upper left and the diagram on the right.

Although not implemented using the Python interactive interface, the code shown in the code window in Figure 3 is similar to code discussed earlier in this module.

Creation of variables and objects

The first two lines of code in Figure 3 show the creation of two variables named x and y and the assignment of the values 6 and 5 to those variables respectively. Thediagram on the right in Figure 3 shows what actually happens in memory as those two lines of code are executed.

The two variables are created and stored in something called the Global frame . Two objects of type int are created and values of 6 and 5 are stored in those objects. The objects themselves are stored in a partof memory commonly called the heap .

The important point

Now here is the important point. The values of 6 and 5 are not actually stored in the variables. Instead, references (sometimes called pointers) that point to the objects containing the values of 6 and 5 are stored in thevariables. Those references can later be used to find and to access the contents of the objects.

The sum of two variables

The statement on line 3 in Figure 3 creates a new variable named z on the left side of the assignment operator. The expression on the right side of theassignment operator accesses the contents of the first two objects, adds their values, and assigns the result to the variable named z . This in turn causes a new object of type int

  • to be created,
  • populated with a value of 11 (the sum of 6 and 5) , and
  • stored on the heap.

A reference to the new object is stored in the new variable named z .

Assigning the same value To several variables

The statement on line 4 in Figure 3 creates three more variables named a, b, and c and assigns a value of 10 to each of them. The diagram on the rightindicates that a single new object of type int containing the value 10 is created and stored on the heap. References to that single object are stored inall three variables named a, b, and c. In other words, the contents of all threevariables point to the same object.

Finally, on line 5, a value of 10 is stored in a new variable named d . The diagram on the right shows that a reference to the existing object containingthe value 10 is stored in this variable as well. Thus, this variable shares an object with the variables named a , b , and c .

Breaking a reference to an object

Figure 4 shows what happens if a different value is assigned to an existing variable. In this case, the string value "ok" is assigned to the existing variablenamed b by the last statement in the code in Figure 4 .

Figure 4. Assign a different value to the variable named b.

missing image

The diagram on the right in Figure 4 shows that this causes a new object of type str

  • to be created,
  • populated with "ok", and
  • stored on the heap.

Questions & Answers

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
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
characteristics of micro business
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
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.
what is the actual application of fullerenes nowadays?
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.
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.
is Bucky paper clear?
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.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Mueller Reply
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