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Program output

The output from this program is shown in Figure 1 .

Figure 1 . Program output.
Print index value 2 A stringPrint a short slice [3.14, 59, 'A string']Print the entire list [3.14, 59, 'A string', 1024]

Visualize sliced lists

Create new lists by slicing an existing list

Figure 2 shows the output from the code visualizer for code similar to the code in Listing 4 . Instead of accessing the list elements and printing them on the fly as in Listing 4 , the code in Figure 2 accesses the list elements and saves references to them so that we can see what the resulting lists look like.

Figure 2. Visualize sliced lists.

Visualize sliced lists.

The diagram on the right in Figure 2 shows the state of the program in memory following the execution of all the code in the code box on the left. Asyou can see, there are now three separate lists:

  • the original list pointed to by the variable named theList and
  • two new lists pointed to by bList and cList .

The two new lists were created by slicing the original list. The elements in the lists allpoint to the float , int , and str objects that were used to populate the original list.

Figure 2 illustrates a very important concept. Three of the variables shown in the light blue box point to objects of type list. Theelements that populate those list objects point to other objects of the types float , int , and str (This concept is often called indirection.)

Since the two bottom lists were created as slices of the original (top) list, they all point to the same objects at this stage in the execution of theprogram.

Change an item in the original list

Figure 3 shows what happens when one of the elements of the original list object is modified to cause it to point to a different object. (Note the arrow that now points from element 2 in the original list object down the screen to a new str object containing the word "changed" .)

Figure 3. Change an item in the original list.

Change an item in the original list.

The important thing to note here is that the pointers in element 2 in the other twolist objects did not follow suite. In other words, they still point to the original str object containing the words "A string" and they do not point to the new str object containing the word "changed" . Thus, even though the two new list objects werecreated as slices from the original list object, once they are created, they are not dependent on thecontents of the original list object. Subsequent changes in the contents of the original list object are not reflected in the contents of the two newlist objects.

Lists can be concatenated

Lists can be concatenated using the + operator.

A concatenation program

The Python program shown in Listing 5 creates two lists and prints them both. Then it concatenates the two lists and prints the concatenated version.

Listing 5 . Lists can be concatenated.
# Illustrates concatenating lists ##------------------------------- print("Create two lists")listA = [3.14,59,"A string",1024] listB = [2,4,6,16]print("Print listA") print(listA)print("Print listB") print(listB)print("Concatenate the lists") listC = listA + listBprint("Print concatenated list") print(listC)

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
Berger describes sociologists as concerned with
Mueller 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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