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Figure 3 shows the output from the code in Listing 2 .

Figure 3 . Output from the code in Listing 2.
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 = ['A', 'new', 'list']

Listing 2 has two major modifications relative to Listing 1 . First, the function returns a copy of the reference to the new list instead ofreturning nothing. Second, the return value is assigned to the variable named bList . This does cause the variable named bList to point to a different list object. This is confirmed by the last line of text in Figure 3 .

Conclusion -- function parameters in Python are passed by value, but the copies that arepassed can often be used to access and modify the objects pointed to by the original reference variables of which they are copies.

In this program, the function's second argument is of no consequence. The function and the program would behave the same if the second argument wereeliminated entirely. I left it in for illustration purposes only.

Hopefully you can study these two programs along with the program output and the above discussion to understand the basic behaviorof Python function arguments.

Required arguments

Note that there is a subtle technical difference between arguments and parameters. However, I often tend to use the two terms interchangeably so you will simplyneed to grit your teeth and bear with me if you see me using one or the other term incorrectly.

When a function defines one or more arguments using the syntax shown in Listing 1 and Listing 2 , the code that calls the function must pass one parameter for each argument and must pass them in the correct order. That is why we call them required arguments . There isn't a lot more that needs to be said about required arguments.

Default arguments

A function can define one or more default arguments in addition to required arguments as shown in Listing 3 . Default values are defined for the default arguments when the function is defined using the syntax shown in Listing 3 .

The calling program can ignore some or all of the default arguments when calling the function. By this I mean that the calling program can simply notpass parameters for some or all of the default arguments. However, when default arguments are ignored, they must be ignored from right to left in the argumentlist. In other words, the calling program cannot ignore a default argument in the middle of a group of default arguments.

When the calling program ignores default arguments, the defined default values for those arguments are used by the code in the body of the function.

The program shown in Listing 3 illustrates a function with one required argument ( listA ) and three default arguments ( listB , listC , and listD ).

Listing 3 . Illustration of default arguments.
# Illustrates default arguments #-----------------------------------------------------------def listModifier(listA,listB=["B"],listC=["C"],listD=["D"]):"""Illustrates default arguments""" print("In listModifier")listA.append(1.00001) print("listA = " + str(listA))listB.append(2.00002) print("listB = " + str(listB))listC.append(3.00003) print("listC = " + str(listC))listD.append(4.00004) print("listD = " + str(listD))return #End function definitionaList = ["ab","cd","ef"] bList = ["The","old","list"]cList = ["This old house"] dList = ["is falling down"]print("aList = " + str(aList)) print("bList = " + str(bList))print("cList = " + str(cList)) print("dList = " + str(dList))print("Call listModifier") listModifier(aList,bList)print("Back from listModifier") print("aList = " + str(aList))print("bList = " + str(bList)) print("cList = " + str(cList))print("dList = " + str(dList))

Questions & Answers

can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
I'm not sure why it wrote it the other way
I got X =-6
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
Commplementary angles
Idrissa Reply
im all ears I need to learn
right! what he said ⤴⤴⤴
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?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
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
I'm not good at math so would you help me
what is the problem that i will help you to self with?
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
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
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
what is system testing
what is the application of nanotechnology?
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
anybody can imagine what will be happen after 100 years from now in nano tech world
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
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
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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