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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

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
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
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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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