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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

where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
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
hey
Giriraj
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
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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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