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Concatenation program output

The output from this program is shown in Figure 4 . As you can see, the concatenated list contains the elements of both of the individual lists.

Figure 4 . Concatenation program output.
Create two lists Print listA[3.14, 59, 'A string', 1024] Print listB[2, 4, 6, 16] Concatenate the listsPrint concatenated list [3.14, 59, 'A string', 1024, 2, 4, 6, 16]

Visualize concatenated lists

Create a new list by concatenating two existing lists

The diagram in Figure 5 visualizes the state of the program memory after the three statements in the code box have been executed. This code creates twolist objects and then concatenates them into a third list object pointed to by the variable named listC .

Figure 5. Visualize concatenated lists.

Visualize concatenated lists

As you can see in Figure 5 , the elements in the new list object point to the objects originally pointed to by the elements in the twooriginal list objects. As you can also see, the order of the elements in the two parts of the new list object preserve theorder of the elements in the two original list objects.

Change an element in an original list

The code in Figure 6 was updated with one additional statement that causes element 0 in one of the original list objects to point to a differentobject of type str containing " OK ".

Figure 6. Change an element in an original list.

Change an element in an original list.

However, element 0 in the concatenated list object pointed to by listC continues to point to the object of type float containing 3.14. The important thing to note here is that the pointer in element 0 in the new list object did not follow suite whenthere was a change in one of the elements in one of the original list objects. It still points to the original float object containing 3.14 and it does not point to the new str object containing "OK" . Therefore, even though the new list object was created by concatenating two original list objects, once created, it is not dependent on thefuture contents of the original list objects. Subsequent changes in the contents of the original list objects are not reflected in the contents of the new list object.

Lists are mutable

Unlike strings, the values in a list can be modified after the list is created.

The Python program shown in Listing 6 creates and prints a list. Then it uses a subscription to modify and print the list three times.

Listing 6 . Lists are mutable.
# Illustrates mutating lists ##------------------------------- print("Create and print a list")listA = [3.14,59,"A string",1024] print(listA)print("Modify the list") listA[2]= "New string" print("Print the modified list")print(listA) print("Modify the list again")listA[3] = listA[3]* 2 print("Print the modified list")print(listA) print("Modify the list again")listA[2] = 0.99999print("Print the modified list") print(listA)

Replace a string with another string

The first modification replaces an existing string in the list with a new string.

Multiply an integer element by two

The second modification multiplies an integer value in the list by a factor of two.

Replace a string by a float

The third modification replaces a string in the list by a float value of 0.99999.

List modification program output

The output from the program is shown in Figure 7 .

Figure 7 . List modification program output.
Create and print a list [3.14, 59, 'A string', 1024]Modify the list Print the modified list[3.14, 59, 'New string', 1024] Modify the list againPrint the modified list [3.14, 59, 'New string', 2048]Modify the list again Print the modified list[3.14, 59, 0.99999, 2048]

More to come

There is a lot more for you to learn about lists that is not included in this module. I will continue this discussion of lists, including moresample programs, in a future module.


This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Itse1359-1080-Lists Part 1
  • File: Itse1359-1080.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

how do you translate this in Algebraic Expressions
linda Reply
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Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
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abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
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Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
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what is system testing
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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
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I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
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Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
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