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Listing 3 . Blank lines and whitespace.
a = 3 # spaces and commentb = 4 # tab and commentc = (a # continue on next line + b)# a blank line follows print(c)# the output is 7

Indentation

In every other programming environment that I have worked with in the past, indentation is used strictly for cosmetic or readability purposes.

However, indentation is not used strictly for cosmetic or readability purposes in Python. It is such an important topic in Python that I haveseparated it into a major section in this module.

Indentation is used to determine grouping of statements

Unlike most other programming environments, physical indentation is used in Python to determine the grouping of statements.

A blessing and a curse

This can be both a blessing and a curse. The blessing is that it forces you to use proper indentation, which usually leads to more readable code.

The curse is that if you don't use proper indentation, your script probably won't behave properly.

No safety nets

There are few if any safety nets in Python (such as the matching curly brackets used in C, C++, and Java) to protect you from indentation errors.

To make matters worse, such errors often turn up as logical errors (meaning that the script simply doesn't work correctly) rather than interpreter errors (meaning that the interpreter will tell you about the error) .

An example of correct indentation

Although I haven't introduced you to the if statement yet, you probably have a fairly good idea what it is used for. I am going to use it to illustrate theproper indentation of a group of statements with the script in Listing 4 .

Description of an "if" statement:

An if statement means that if some expression evaluates to true , the program will do something specific. Otherwise, the script won't do that specificthing.

Don't be too concerned if the logic of the script in Listing 4 escapes you at this point in time. I will explain the use of the if statement in detail in a futuremodule. The important thing here is to understand the grouping of statements.

Listing 4 . An example of correct indentation.
A = 3 B = 4if B>A: print(A) # begin groupprint(B) print(A + B) # end groupA = 6 # not part of above group print(A)#============================================================ #The output, which is not part of the script, is shown below.3 47 6

Compare A with B and take appropriate action

The script in Listing 4 compares the value of the variable A with the value of the variable B to determine if the value of B is greater than the value of A (if B>A:) .

If the value of B is greater than the value of A (which it is in this case) , the three indented print statements are executed. Otherwise, that group of threestatements is bypassed.

A compound statement

The three statements shown with indentation are either all executed, or they are all bypassed. Hence, they behave as a group.

A group of statements like this is sometimes referred to as a compound statement (a statement made up of two or more individual statements) .

Group behavior

When the three indented statements are executed as a group, the values 3, 4, and 7 are printed on consecutive output lines by the three print statements in the groupof statements, as shown in Figure 2 .

Questions & Answers

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
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
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
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit 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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