What will be output of the code:
def gfg(x,l=[]):
for i in range(x):
l.append(i*i)
print(l)
What is the output of following function calls-
gfg(3,[3,2,1])
gfg(3)
First of all welcome to stackoverflow! For the following code it's probably best to just try to run your code in a python shell and see the output. But I can provide some explanation as to why you get the output that you do.
Your code was as follows:
def gfg(x, l=[]):
for i in range(x):
l.append(i*i)
print(l)
And we are trying to run this function on the following input:
gfg(3, [3,2,1]) and gfg(3).
The output that we get is as follows:
gfg(3, [3,2,1]) = [3,2,1,0,1,4]
gfg(3) = [0,1,4]
This is because python uses something called default arguments that are used when we do not pass in the required number of arguments into a function. So in the first case when we print out l we get that 0,1,4 is appended onto the end of the existing parameter l that is passed into the function ([3,2,1]. And when we do not pass in an argument for l the output is just the list [0,1,4].
Related
<code>def CheckNumber(MyList, number):
counter=0
while number!=0:
for i,element in enumerate(MyList):
if number%10==element:
del MyList[i]
else:
continue
number = number/10
if len(MyList)==0:
return 1
else:
return 2
print("Program to print all the possible combinations of a number")
MyNumber = int(input("Enter the number: "))
MyList = []
while MyNumber!=0:
MyList.append(MyNumber%10)
MyNumber=int(MyNumber/10)
MyLimit = 10**(len(MyList)-1)
for i in range(MyLimit, MyLimit*10):
answer = CheckNumber(MyList, i)
if answer == 1:
print(i)
else:
continue`</code>
I am a beginner at programming and I was trying to write a code to print all the possible combinations of a number. If user enters a 3 digit number the program will check all the three digit numbers to find possible combinations but instead it gives all the numbers as output. For example if user enters 12 then the output should be 12 21 but instead it shows every number from 10 to 99.
As far as I know everything is working fine but the results are not as I expect.
This is a pass-by-reference vs pass-by-value problem. What that means is when you pass a list to a function in python you are not passing the values in that list, you are passing the list itself, or rather its location in memory. So when you are modifying MyList in your CheckNumber function you are actually modifying the MyList variable globally. This is not true for primitive types which is why modifying number does not change i in the for loop. Quick example:
def foo(my_list):
my_list.append('world')
print(my_list)
a = []
foo(a) # this will print out 'world'
print(a) # this will print out 'world'
b = 'hello'
foo(b.copy()) # This will print out 'hello world'
print(b) # Here we have not passed b directly into foo,
# but instead passed a copy, so this will just print out 'hello' as b
# has not been modified
To summarize variable are stored in a specific location in memory. When you pass-by-reference you are passing a long that location in memory so you variable will be mutated. If you pass-by-value, you function will create a new variable and store a copy of the data so you will not mutate your outer variable. In other languages you can specify which way to pass in a variable but afaik you cannot in python.
With that out of the way this is a very easy fix. You don't want to modify your original MyList so just make a copy of it and pass that into the function. You also forgot to cast number/10 to int in the CheckNumber function. The working code should look like this:
def CheckNumber(MyList, number):
counter=0
while number!=0:
for i,element in enumerate(MyList):
if number%10==element:
del MyList[i]
else:
continue
number = int(number/10)
if len(MyList)==0:
return 1
else:
return 2
print("Program to print all the possible combinations of a number")
MyNumber = int(input("Enter the number: "))
MyList = []
while MyNumber!=0:
MyList.append(MyNumber%10)
MyNumber=int(MyNumber/10)
MyLimit = 10**(len(MyList)-1)
for i in range(MyLimit, MyLimit*10):
answer = CheckNumber(MyList.copy(), i)
if answer == 1:
print(i)
else:
continue
More info on pass-by-reference:
What's the difference between passing by reference vs. passing by value?
https://blog.penjee.com/passing-by-value-vs-by-reference-java-graphical/
https://courses.washington.edu/css342/zander/css332/passby.html
I want to use a random value from the GET method, in the POST method.
List car = Audi, Porsche, Ford, VW, Honda, Citroen
$['carTypes'][0]['carType']['enum']
Result: [Audi]
$['carTypes'][${=(int)(Math.random()*6)}]['carType']['enum']
Result: [Porsche] (random 1 car from the list of 5 available)
I would like to get a list of random cars but not limited to just one car - random list of cars but in the range of 0 to 6, not only 1 value.
Result: [Audi,Porsche]
Result: [Ford, VW, Honda]
Result: [Citroen]
I have tried like this.
$['carTypes'][${=(int)(Math.random()*6)},${=(int)(Math.random()*6)}]['carType']['enum']
Result: [[Citroen, Honda]]
Probably 2 flat brackets [[ prevent me from using this data in the POST method, how to get rid of unnecessary brackets?
Groovy
import groovy.json.JsonOutput
Random random = new Random()
def list = ["Porsche","Ford","VW"]
def randomValue = random.nextInt(list.size())
def list2 = ["Porsche","Ford","VW"]
def randomValue2 = random.nextInt(list2.size())
def theValue = list2[randomValue2] +","+ list[randomValue]
I will be grateful for your help.
Instead of putting the above in your post step, you could create a Groovy script step in between the GET and POST requests.
In the Groovy script, you can then 'build' the string exactly how you want, including the removal of the brackets. The last line in the script should be a return statement that returns the string you built.
In the POST request, you can then 'pull' in the value from the groovy script step using the $ functionality. E.g. ${Groovy Script Name#result}
I'm practicing leetcode and checking other people's solutions for the same exercise on my terminal gives a totally different output than expected. If I run it on leetcode it says the answer is correct...
What might be causing this?
reversing the array of chars - ["h","e","l","l","o"] - like so:
def reverse_string(s)
len = s.length
(0...len/2).each { |i|
temp = s[i]
swap_index = len-i-1
s[i] = s[swap_index]
s[swap_index] = temp
}
end
p reverse_string([["h","e","l","l","o"]])
output in my terminal -- 0...2
output in leetcode is as expected - ["o","l","l","e","h"]
Why does this happen?
thanks
Ruby's p function will print the value you pass to it.
The value you are choosing to pass to it is the return value of reverse_string.
You should add a line to the end of reverse_string that specifies what you want to return from it. In this case the line can simply consist of s. You don't even need an explict return in this case.
I'm trying to create a random number generator in Lua. I found out that I can just use math.random(1,100) to randomize a number between 1 and 100 and that should be sufficient.
But I don't really understand how to use the randomize number as variables in the script.
Tried this but of course it didn't work.
$randomCorr = math.random(1,100);
http.request_batch({
{"POST", "https://store.thestore.com/priceAndOrder/selectProduct", headers={["Content-Type"]="application/json;charset=UTF-8"}, data="{\"ChoosenPhoneModelId\":4,\"PricePlanId\":\"phone\",\"CorrelationId\":\"$randomCorr\",\"DeliveryTime\":\"1 vecka\",\"$$hashKey\":\"006\"},\"ChoosenAmortization\":{\"AmortizationLength\":0,\"ChoosenDataPackage\":{\"Description\":\"6 GB\",\"PricePerMountInKr\":245,\"DataAmountInGb\":6,\"$$hashKey\":\"00W\"},\"ChoosenPriceplan\":{\"IsPostpaid\":true,\"Title\":\"Fastpris\",\"Description\":\"Fasta kostnader till fast pris\",\"MonthlyAmount\":0,\"AvailiableDataPackages\":null,\"SubscriptionBinding\":0,\"$$hashKey\":\"00K\"}}", auto_decompress=true},
{"GET", "https://store.thestore.com/api/checkout/getproduct?correlationId=$randomCorr", auto_decompress=true},
})
In Lua, you can not start a variable name with $. This is where your main issue is at. Once the $ is removed from your code, we can easily see how to refer to variables in Lua.
randomCorr = math.random(100)
print("The random number:", randomCorr)
randomCorr = math.random(100)
print("New Random Number:", randomCorr)
Also, concatenation does not work the way you are implying it into your Http array. You have to concatenate the value in using .. in Lua
Take a look at the following example:
ran = math.random(100)
data = "{\""..ran.."\"}"
print(data)
--{"14"}
The same logic can be implied into your code:
data="{\"ChoosenPhoneModelId\":4,\"PricePlanId\":\"phone\",\"CorrelationId\":\""..randomCorr.."\",\"DeliveryTime\":\"1 vecka\",\"$$hashKey\":\"006\"},\"ChoosenAmortization\":{\"AmortizationLength\":0,\"ChoosenDataPackage\":{\"Description\":\"6 GB\",\"PricePerMountInKr\":245,\"DataAmountInGb\":6,\"$$hashKey\":\"00W\"},\"ChoosenPriceplan\":{\"IsPostpaid\":true,\"Title\":\"Fastpris\",\"Description\":\"Fasta kostnader till fast pris\",\"MonthlyAmount\":0,\"AvailiableDataPackages\":null,\"SubscriptionBinding\":0,\"$$hashKey\":\"00K\"}}"
Or you can format the value in using one of the methods provided by the string library
Take a look at the following example:
ran = math.random(100)
data = "{%q}"
print(string.format(data,ran))
--{"59"}
The %q specifier will take whatever you put as input, and safely surround it with quotations
The same logic can be applied to your Http Data.
Here is a corrected version of the code snippet:
local randomCorr = math.random(1,100)
http.request_batch({
{"POST", "https://store.thestore.com/priceAndOrder/selectProduct", headers={["Content-Type"]="application/json;charset=UTF-8"}, data="{\"ChoosenPhoneModelId\":4,\"PricePlanId\":\"phone\",\"CorrelationId\":\"" .. randomCorr .. "\",\"DeliveryTime\":\"1 vecka\",\"$$hashKey\":\"006\"},\"ChoosenAmortization\":{\"AmortizationLength\":0,\"ChoosenDataPackage\":{\"Description\":\"6 GB\",\"PricePerMountInKr\":245,\"DataAmountInGb\":6,\"$$hashKey\":\"00W\"},\"ChoosenPriceplan\":{\"IsPostpaid\":true,\"Title\":\"Fastpris\",\"Description\":\"Fasta kostnader till fast pris\",\"MonthlyAmount\":0,\"AvailiableDataPackages\":null,\"SubscriptionBinding\":0,\"$$hashKey\":\"00K\"}}", auto_decompress=true},
{"GET", "https://store.thestore.com/api/checkout/getproduct?correlationId=" .. randomCorr, auto_decompress=true},
})
There is something called $$hashKey also, in the quoted string. Not sure if that is supposed to be referencing a variable or not. If it is, it also needs to be concatenated into the resulting string, using the .. operator (just like with the randomCorr variable).
Can you determine at runtime if the executed code is running as a function or a script? If yes, what is the recommended method?
There is another way. nargin(...) gives an error if it is called on a script. The following short function should therefore do what you are asking for:
function result = isFunction(functionHandle)
%
% functionHandle: Can be a handle or string.
% result: Returns true or false.
% Try nargin() to determine if handle is a script:
try
nargin(functionHandle);
result = true;
catch exception
% If exception is as below, it is a script.
if (strcmp(exception.identifier, 'MATLAB:nargin:isScript'))
result = false;
else
% Else re-throw error:
throw(exception);
end
end
It might not be the most pretty way, but it works.
Regards
+1 for a very interesting question.
I can think of a way of determining that. Parse the executed m-file itself and check the first word in the first non-trivial non-comment line. If it's the function keyword, it's a function file. If it's not, it's a script.
Here's a neat one-liner:
strcmp(textread([mfilename '.m'], '%s', 1, 'commentstyle', 'matlab'), 'function')
The resulting value should be 1 if it's a function file, and 0 if it's a script.
Keep in mind that this code needs to be run from the m-file in question, and not from a separate function file, of course. If you want to make a generic function out of that (i.e one that tests any m-file), just pass the desired file name string to textread, like so:
function y = isfunction(x)
y = strcmp(textread([x '.m'], '%s', 1, 'commentstyle', 'matlab'), 'function')
To make this function more robust, you can also add error-handling code that verifies that the m-file actually exists before attempting to textread it.