<< Chapter < Page Chapter >> Page >

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

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
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Berger describes sociologists as concerned with
Mueller Reply
Got questions? Join the online conversation and get instant answers!
QuizOver.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