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More on nested elements

The program in Listing 4 illustrates some additional aspects of nested elements.

Listing 4 . More nested elements.
# Illustrates more nested elements ##----------------------------------------- print("Create and print a list\with 3 nested elements") listA = [[2,4],[8,16,32],[64,128,256,512]]print(listA) print("Number of elements is:")print(len(listA)) print("Length of Element 0 is")print(len(listA[0]))print("Length of Element 1 is") print(len(listA[1])) print("Length of Element 2 is")print(len(listA[2]))

Create a list of lists

This program defines a three-element list containing three nested lists.

In other words, each of the elements in the outer list is itself a list.

Inner lists are different lengths

Furthermore, the lengths of the inner nested lists are not the same. The lengths of the inner nested lists are 2, 3, and 4 elements each, respectively.

Program behavior and output

The output from the program is shown in Figure 5 . The program displays the entire list, and then gets and displays the lengths of each of the nested lists.

Figure 5 . Output from more nested elements.
Create and print a list with 3 nested elements [[2, 4], [8, 16, 32], [64, 128, 256, 512]]Number of elements is: 3Length of Element 0 is 2Length of Element 1 is 3Length of Element 2 is 4

Getting the length of a nested list

Note in particular the syntax used to pass a parameter to the len() method in order to get the length of a nested list (len(listA[1]) ) .

Arrays -- not for beginners

If you are a beginning programmer, you may want to skip this section. If you are an experienced programmer, you may have observed that a Python lists bear a striking resemblance to arrays in other programming environments.

Python lists are more powerful

However, Python lists are more powerful than the arrays I am aware of in other programming environments, including Java.

Sub-arrays can be different sizes

For example as in Java, when a Python list is used to construct a multidimensional array, the sub arrays don't have to be of the same size.

Types can also be different

However, unlike Java, the elements in the array don't even have to be of the same type (granted that the elements in a Java array can be of different types so long as there is an inheritance or Interface relationship among them).

A three-dimensional array program

The program in Listing 5 might represent what an experienced programmer would consider to be athree-dimensional array of integer data in some other programming environment.

Listing 5 . A three-dimensional array program.
# Illustrates a three-dimensional array list ##---------------------------------------------------- print("Create and print a\three-dimensional array list") listA = [[[[1],[2]],[[3],[4]]],[[[5],[6]],[[7],[8]]]] print(listA)print("Print each element") print(listA[0][0][0]) print(listA[0][0][1]) print(listA[0][1][0]) print(listA[0][1][1]) print(listA[1][0][0]) print(listA[1][0][1]) print(listA[1][1][0]) print(listA[1][1][1])

Triple-square-bracket notation

Pay particular attention to the triple square bracket notation that is used to access and print each element in the array. This is very similar to thesyntax in other programming languages.

Visualization of a three-dimensional array

Figure 6 shows a visualization of the three-dimensional array pointed to by the variable named listA in Listing 5 . In programming, we deal with arrays having one, two, three or more dimensions. As you can see, even a three-dimensional array is arelatively complex structure.

Figure 6. Visualization of a three-dimensional array.

Visualization of a three-dimensional array.

Program behavior

This program

  • Creates and populates the list that represents a three-dimensional array.
  • Displays the entire array as a set of nested lists.
  • Displays the contents of each element in the array.

Output from a three-dimensional array program

The output from the program is shown in Figure 7 . The triple-square-bracket notation in the program of Listing 5 is essentially the same notation that would be used to access the individual elements in athree-dimensional array in C, C++, or Java.

Figure 7 . Output from a three-dimensional array program.
Create and print a three-dimensional array list [[[[1], [2]], [[3], [4]]], [[[5], [6]], [[7], [8]]]] Print each element[1] [2][3] [4][5] [6][7] [8]

More information on lists

There is quite a lot more that you will need to learn about lists. However, I will defer that discussion for a future module where I discuss the use of a listas a data structure or a container .


This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Itse1359-1090-Lists Part 2
  • File: Itse1359-1090.htm
  • Published: 10/15/14
  • Revised: 01/31/16

Financial : Although the Connexions site makes it possible for you to download a PDF file for thismodule at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should beaware that some of the HTML elements in this module may not translate well into PDF.

I also want you to know that, I receive no financial compensation from the Connexions website even if you purchase the PDF version of the module.

In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.com showing me as the author. Ineither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, please beaware that it is a copy of a module that is freely available on cnx.org and that it was made and published withoutmy prior knowledge.

Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.


Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
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
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
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.
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
for teaching engĺish at school how nano technology help us
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
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?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
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
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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