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You can later retrieve the values that you have stored there by referring to the pigeonhole by its nickname ( identifier ). You can also store a different value in the pigeonhole later if you desire.

The concept of type

Strongly typed languages

One of the main differences between Python and programming languages such as Java and C++ is the concept of type .

In strongly-typed languages like Java and C++, variables not only have a name, they also have a type. The type determines the kind of data that you can store in thepigeonhole.

It is probably more correct to say that the type determines the values that you can store there and the operations (addition, subtraction, etc.) that you can perform on those values.

Python is not strongly typed

One of the characteristics that makes Python easier to use than Java is the fact that with Python you don't have to be concerned about the type of avariable. Python takes care of type issues for you behind the scenes. However that ease of use comes with some costs attached.

Declaration of variables

Another difference between Python and Java is that with Java, you must declare variables before you can use them. Declaration of variables is not required with Python.

With Python, if you need a variable, you simply come up with a name and start using it as a variable.

Dangerous curves ahead !

With this convenience comes some danger. You can only have one variable with the same name within the same scope (I will discuss scope in a future module) .

Don't use the same name for two variables

With Python, if you unintentionally use the same name for two or more variables, the first will be overwritten by the second. This can lead to program bugs that aredifficult to find and fix.

A more subtle danger

A more subtle danger is that you create a variable that you intend to use more than once and you spell it incorrectly in one of those uses. This can be anextremely difficult problem to find and fix. I will illustrate what I mean by this later with a sample program.

Rules for identifiers

The name for a variable must follow the naming rules for identifiers that you will find in the Python Language Reference -- 2.3. Identifiers and keywords .

Give me the rules in plain English

The notation used in the Python Language Reference to define the naming rules is a little complicated, so I will try to interpret it for you.

Allowable characters

I believe that the Python Language Reference -- 2.3. Identifiers and keywords is saying that identifiers must begin with either a letter or an underscore character. Following that, you can use anunlimited sequence of letters (uppercase A through Z or lowercase a through z) , numbers (0 through 9) , or underscore characters.

Note that although the underscore character is allowed, it has special meaning in Python. I recommend that you do not use the underscorecharacter for the identifiers that you create.

Case is significant

The letters can be uppercase or lowercase, and case is significant. In other words, the identifier Ax is not the same as the identifier aX .

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
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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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