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If a parameter is passed by reference, the incoming parameter can be used by code in the function to modify the original. Some programming languages supportboth types of parameter passing.

According to tutorialspoint -- Python Functions , all parameters in Python are passed by reference . On the other hand, according to The Python Tutorial -- Defining Functions ,

"thus, arguments are passed using call by value (where the value is always an object reference, not the value of the object)."

In this case, I come down on the side of call by value . I think it is more correct to say that parameters are passed by value and as a result, thefunction receives copies of references to objects. Even though I can use a copy of an object's reference to modify the object, I cannot use a copy of thatreference to cause the original reference to point to a different object. I can modify the object to which the reference points, but I cannot modify thereference itself.

I will illustrate what I mean by this in conjunction with the program in Listing 1 .

Discussion and sample code

This module will examine the following kinds of arguments:

  • Required arguments
  • Default arguments
  • Keyword arguments
  • Variable-length arguments

Passing by value or reference

The program shown in Listing 1 illustrates the significance of passing parameters by value or by reference when those parameters are references to objects. Listing 1 also illustrates the use of two required arguments .

Listing 1 . A list-modifier function.
# Illustrates pass by value or reference #---------------------------------------------------def listModifier(listA,listB): """Illustrates pass by value or reference"""print("In listModifier") print("Use incoming parameter to append to listA")listA.append(3.14159) print("New listA = " + str(listA))print("Assign a new list to listB") listB = ["A","new","list"]print("New listB = " + str(listB)) return#End function definition #Call the functionprint("Create two lists") aList = ["ab","cd","ef"]bList = ["The","old","list"] print("aList = " + str(aList))print("bList = " + str(bList)) print("Call listModifier")listModifier(aList,bList) print("Back from listModifier")print("aList = " + str(aList)) print("bList = " + str(bList))

Figure 1 shows the output produced by the code in Listing 1 .

Figure 1 . Output from the code in Listing 1.
Create two lists aList = ['ab', 'cd', 'ef']bList = ['The', 'old', 'list'] Call listModifierIn listModifier Use incoming parameter to append to listANew listA = ['ab', 'cd', 'ef', 3.14159] Assign a new list to listBNew listB = ['A', 'new', 'list'] Back from listModifieraList = ['ab', 'cd', 'ef', 3.14159] bList = ['The', 'old', 'list']

The function definition

The code in Listing 1 defines a function named listModifier . This function receives two incoming parameters. Each parameter points to adifferent list. I contend that the incoming parameters are actually copies of the variables that were passed as parameters.

The code in the function uses one of the incoming parameters to access the list and to append a value of 3.14159 onto the end of the list. The second line of text from the bottom of Figure 1 confirms that this operation was successful.

Questions & Answers

can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
Commplementary angles
Idrissa Reply
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
is it 3×y ?
Joan Reply
J, combine like terms 7x-4y
Bridget Reply
im not good at math so would this help me
Rachael Reply
yes
Asali
I'm not good at math so would you help me
Samantha
what is the problem that i will help you to self with?
Asali
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris 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
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
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
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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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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