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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

I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
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
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
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
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
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
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
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
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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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