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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

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.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
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
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
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
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
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
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
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
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.
Ali Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
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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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