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An important and potentially confusing point

At the risk of becoming boring, there is an important point here that you might as well get used to right now.

The s is located at index value 3. However, according to the way you are probably accustomed to counting, this is actually the fourth character in thestring. You might be inclined to refer to this character as character number 4.

This is because index values always begin with zero, while you are probably accustomed to counting things beginning with one, not zero.

Not like eggs

Regardless of whether you begin with zero or one, if you access the egg at index value 4 in the container and eat it for breakfast, it cannot be accessed again (because it will be gone) .

However, if you access the character at index value 4 in the string and use it for some purpose, what you really use is a copy of the character. It is stillthere and it can be accessed again.

(Some data containers do allow for the removal of data elements in much the same sense that we can remove an egg from its container. However, a string isnot such a container.)

A simple slice

The fragment in Listing 2 cuts a couple of slices out of the string that was created in Listing 1 and displays them on the screen.

Listing 2 . A simple slice.
print(aStr[0:4]) #print Thisprint(aStr[10:16]) #print string

Slice notation

The slice notation uses two index values separated by a colon, as shown in Listing 2 .

The end is non-inclusive

As was indicated in the earlier quotation, "... the end is non-inclusive." This means that the character whose index value is the number following thecolon is not included in the slice.

Extract the first word in the string

Thus, the first statement in Listing 2 containing the reference aStr[0:4] extracts and prints the character sequence beginning with index value 0 and ending with indexvalue 3 (not 4) . This causes the word This to be extracted and printed.

Extract the last word in the string

Similarly, the second statement in the above fragment containing the reference aStr[10:16] extracts and prints the characters having index values from 10 through 15, inclusive (not 16) . This causes the word string to be extracted and printed.

A more complicated slice

Omitting the first index

If you omit the first index value, as shown in Listing 3 , it defaults to the value zero.

Listing 3 . Omitting the first index.
print(aStr[:4]) #print This

Therefore, the statement in Listing 3 extracts and prints the first word in the string, which is This .

Omitting the second index

If you omit the second index, as shown in Listing 4 , it defaults to a value that includes the last character in the string.

Listing 4 . Omitting the second index.
print(aStr[10:]) #print string

Thus, the statement in Listing 4 extracts and prints the last word in the string, which is string .

Listing 5 shows two different ways to extract and print the entire string. I won't comment on this, but will leave the analysis as an exercise for thestudent.

Listing 5 . Print the entire string.
#print the entire string print(aStr[:5]+ aStr[5:])print(aStr[:100])

Questions & Answers

the diagram of the digestive system
Assiatu Reply
allimentary cannel
Ogenrwot
How does twins formed
William Reply
They formed in two ways first when one sperm and one egg are splited by mitosis or two sperm and two eggs join together
Oluwatobi
what is genetics
Josephine Reply
Genetics is the study of heredity
Misack
how does twins formed?
Misack
What is manual
Hassan Reply
discuss biological phenomenon and provide pieces of evidence to show that it was responsible for the formation of eukaryotic organelles
Joseph Reply
what is biology
Yousuf Reply
the study of living organisms and their interactions with one another and their environments
AI-Robot
the study of living organisms and their interactions with one another and their environment.
Wine
discuss the biological phenomenon and provide pieces of evidence to show that it was responsible for the formation of eukaryotic organelles in an essay form
Joseph Reply
what is the blood cells
Shaker Reply
list any five characteristics of the blood cells
Shaker
lack electricity and its more savely than electronic microscope because its naturally by using of light
Abdullahi Reply
advantage of electronic microscope is easily and clearly while disadvantage is dangerous because its electronic. advantage of light microscope is savely and naturally by sun while disadvantage is not easily,means its not sharp and not clear
Abdullahi
cell theory state that every organisms composed of one or more cell,cell is the basic unit of life
Abdullahi
is like gone fail us
DENG
cells is the basic structure and functions of all living things
Ramadan
What is classification
ISCONT Reply
is organisms that are similar into groups called tara
Yamosa
in what situation (s) would be the use of a scanning electron microscope be ideal and why?
Kenna Reply
A scanning electron microscope (SEM) is ideal for situations requiring high-resolution imaging of surfaces. It is commonly used in materials science, biology, and geology to examine the topography and composition of samples at a nanoscale level. SEM is particularly useful for studying fine details,
Hilary
cell is the building block of life.
Condoleezza Reply
what is cell divisoin?
Aron Reply
Diversity of living thing
ISCONT
what is cell division
Aron Reply
Cell division is the process by which a single cell divides into two or more daughter cells. It is a fundamental process in all living organisms and is essential for growth, development, and reproduction. Cell division can occur through either mitosis or meiosis.
AI-Robot
What is life?
Allison Reply
life is defined as any system capable of performing functions such as eating, metabolizing,excreting,breathing,moving,Growing,reproducing,and responding to external stimuli.
Mohamed
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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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