<< Chapter < Page Chapter >> Page >

Command line versus GUI

The text in Figure 4 was produced using the Python (command line) interface. I don't get exactly the same behavior (with respect to prompts) when I use the Python GUI interface. Rather, what I get is shown in Figure 3 . (Note the missing ... prompt.)

The difference between the ... prompt and the>>>prompt is discussed in section 2.1.2. Interactive Mode of The Python Tutorial . (Note that the tutorial is also accessible in a different format from the Start/All Programs/Python 3.4 selection in Windows.)

Apparently the command-line interface creates the ... prompt when it thinks that the next line is a continuation line. The example given in the tutorial isshown in Figure 5 . (Don't be concerned if you don't understand the code in Figure 5 . I will explain similar code in a future module.)

Figure 5 . Example prompts from The Python Tutorial.
>>>the_world_is_flat = True>>>if the_world_is_flat: ... print("Be careful not to fall off!")... Be careful not to fall off!

Apparently for the case of Figure 4 , the system became confused by the comment and treated the line after the comment as a continuation line.

The IDLE GUI did not become confused in Figure 3 . I believe that it accomplishes line continuation by automatically indenting the next line and nocontinuation was required in either Figure 3 or Figure 4 .

Let's get technical

But not too technical. Computer programs are made up of statements.

Statements are composed of expressions.

(Later we will learn that large Python programs are made up of smaller programs called modules, which are made up of statements, which are composed ofexpressions.)

Statement ends at the end of the line

In Python, a statement normally ends at the end of the line that contains it (although there are exceptions to this rule) .

For the time being, suffice it to say that expressions are made up of

  • literal values
  • variables
  • operators
  • parentheses

Literal values and variables

Literal values are simply numbers that are included in an expression such as the 2 and the 5 shown in Figure 3 .

I will defer a discussion of variables until a future module, and will discuss operators and parentheses in the following paragraphs.

Operators

If you have ever used a hand calculator, you already know what operators are. The plus key on a hand calculator is an operator. The plus sign (+) in the expression shown in Figure 6 is also an operator.

Figure 6 . A Python addition operator.
>>>2+5

In programming jargon, operators are said to operate on operands ..

Operands

In Figure 6 , the 2 is the left operand and the 5 is the right operand of the + operator.

Unary and binary operators

Normally, operators are said to be either unary or binary .

A unary operator has only one operand while a binary operator has two operands.

Some can be either

Some operators, such as the minus sign (-), can be either unary or binary operators.

In its unary mode with a single operand, a minus sign is usually a sign changing operator, while in its binary mode with two operands, a minus sign is usually a subtraction operator.

Questions & Answers

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
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
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
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
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.
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 did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!





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
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Itse 1359 introduction to scripting languages: python' conversation and receive update notifications?

Ask