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Forcing multiplication to be performed first

In the second expression, the code in Figure 12 forced Python to perform the multiplication first (which it does anyway by default, but the parentheses make that more obvious) . This produced an intermediate value of 20. The remaining part of the overallexpression was then evaluated by adding the intermediate value to 3 producing an output of 23.

Hopefully, you get the picture. By using parentheses to group the terms in an expression, you have total control over the order in which the arithmeticoperations are performed, without having to memorize a precedence table.

Nested parentheses

Parentheses can be, and often are nested to provide greater control over the order of the operations as shown in Figure 13 .

Figure 13 . Nested parentheses.
>>>(3+(5*4))*14 # nested parentheses 322>>>

In this case, Python evaluates the expressions inside the innermost parentheses first, and then works from the inside out evaluating each pair ofparentheses along the way.

Negative integer division

When I learned to do long division in the second grade, I didn't know about positive and negative numbers yet, so I didn't learn about remainders when oneof the operands is negative and the other is positive. I suspect that you didn't either.

Figure 14 shows how negative integer division and modulus works in Python.

Figure 14 . Negative integer division.
>>>7 // -3 -3>>>7 % -3 -2>>>7 // 3 2>>>7 % 3 1>>>

You may find these results surprising. I'm not going to try to explain it. I just want to make you aware that the behavior of integer division and integer modulus is different when the operandshave different signs. I will leave it as "an exercise for the student" to think about this and come to a mental reconciliation with the facts as presented here.

Complex numbers

Python also provides a significant level of support for doing arithmetic with complex numbers. Since this is a very specialized area, which is probably ofinterest to only a small percentage of potential Python users, I'm not going to provide any of the details. If this is something that interests you, see Standard Library -- Mathematical functions for complex numbers for more information.

Programming errors

Sometimes, you may make an error and enter an expression that can't be evaluated. In this case, you will get an error message. A typical error messagethat was produced by the command-line interface is shown in Figure 15 .

Figure 15 . An error on the command-line interface.
>>>3 + 5a File "<stdin>", line 1 3 + 5a^ SyntaxError: invalid syntax>>>

Note that the IDLE GUI interface doesn't provide as much information as the command-line interface for the same error. Only the SyntaxError message appears on the IDLE GUI interface as shown in Figure 16 .

Figure 16 . An error on the IDLE GUI interface.
>>>3 + 5a SyntaxError: invalid syntax>>>

Not shown here, however, is the fact that the 5a is highlighted with a red background in the GUI interface. Also, the error message is displayed inred.

Referring back to Figure 15 , this error message means that the Python interpreter doesn't know how to add the value 3 to the value 5a. I will discuss error messages in moredetail in a future module. I just wanted to show you a programming error here at the beginning. (Note the ^ character in Figure 15 pointing upward to the "a"character. This is a pointer to the source of the error.)

Miscellaneous

This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Itse1359-1020-Numbers
  • File: Itse1359-1020.htm
  • Published: 10/14/14
  • Revised: 03/26/15
Disclaimers:

Financial : Although the Connexions site makes it possible for you to download a PDF file for thismodule at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should beaware that some of the HTML elements in this module may not translate well into PDF.

I also want you to know that, I receive no financial compensation from the Connexions website even if you purchase the PDF version of the module.

In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.com showing me as the author. Ineither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, please beaware that it is a copy of a module that is freely available on cnx.org and that it was made and published withoutmy prior knowledge.

Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.

-end-

Questions & Answers

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
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
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
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
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
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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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