How can I get my function to add together its output?

Question

So this is my line of code so far,

def Adder (i,j,k):
    if i<=j:
        for x in range (i, j+1):
            print(x**k)
    else:
        print (0)

What it's supposed to do is get inputs (i,j,k) so that each number between [i,j] is multiplied the power of k. For example, Adder(3,6,2) would be 3^2 + 4^2 + 5^2 + 6^2 and eventually output 86. I know how to get the function to output the list of numbers between i and j to the power of K but I don't know how to make it so that the function sums that output. So in the case of my given example, my output would be 9, 16, 25, 36.

Is it possible to make it so that under my if conditional I can generate an output that adds up the numbers in the range after they've been taken to the power of K?

If anyone can give me some advice I would really appreciate it! First week of any coding ever and I don't quite know how to ask this question so sorry for vagueness!

Question now Answered, thanks to everyone who responded so quickly!

Answer 1

You could use built-in function sum()

def adder(i,j,k):
    if i <= j:
        print(sum(x**k for x in range(i,j+1)))
    else:
        print(0)

The documentation is here

Answer 2

Looking at a few of the answers posted, they do a good job of giving you pythonic code for your solution, I thought I could answer your specific questions:

How can I get my function to add together its output?

A perhaps reasonable way is to iteratively and incrementally perform your calculations and store your interim solutions in a variable. See if you can visualize this:

Let's say (i,j,k) = (3,7,2) We want the output to be: 135 (i.e., the result of the calculation 3^2 + 4^2 + 5^2 + 6^2 + 7^2)

Use a variable, call it result and initialize it to be zero.

As your for loop kicks off with x = 3, perform x^2 and add it to result. So result now stores the interim result 9. Now the loop moves on to x = 4. Same as the first iteration, perform x^2 and add it to result. Now result is 25. You can now imagine that result, by the time x = 7, contains the answer to the calculation 3^2+4^2+5^2+6^2. Let the loop finish, and you will find that 7^2 is also added to result.

Once loop is finished, print result to get the summed up answer.

A thing to note:

Consider where in your code you need to set and initialize the _result_ variable.

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If anyone can give me some advice I would really appreciate it! First week of any coding ever and I don't quite know how to ask this question so sorry for vagueness!

Perhaps a bit advanced for you, but helpful to be made aware I think:

Alright, let's get some nuance added to this discussion. Since this is your first week, I wanted to jot down some things I had to learn which have helped greatly.

Iterative and Recursive Algorithms

First off, identify that the solution is an iterative type of algorithm. Where the actual calculation is the same, but is executed over different cumulative data. In this example, if we were to represent the calculation as an operation called ADDER(i,j,k), then:

ADDER(3,7,2) = ADDER(3,6,2)+ 7^2

ADDER(3,6,2) = ADDER(3,5,2) + 6^2

ADDER(3,5,2) = ADDER(3,4,2) + 5^2

ADDER(3,4,2) = ADDER(3,3,2) + 4^2

ADDER(3,3,2) = 0 + 3^2

Problems like these can be solved iteratively (like using a loop, be it while or for) or recursively (where a function calls itself using a subset of the data). In your example, you can envision a function calling itself and each time it is called it does the following:

1. calculates the square of j and
2. adds it to the value returned from calling itself with j decremented by 1 until
3. j < i, at which point it returns 0

Once the limiting condition (Point 3) is reached, a bunch of additions that were queued up along the way are triggered.

Learn to Speak The Language before using Idioms

I may get down-voted for this, but you will encounter a lot of advice displaying pythonic idioms for standard solutions. The idiomatic solution for your example would be as follows:

def adder(i,j,k):
  return sum(x**k for x in range(i,j+1)) if i<=j else 0

But for a beginner this obscures a lot of the "science". It is far more rewarding to tread the simpler path as a beginner. Once you develop your own basic understanding of devising and implementing algorithms in python, then the idioms will make sense.

Just so you can lean into the above idiom, here's an explanation of what it does:

It calls the standard library function called sum which can operate over a list as well as an iterator. We feed it as argument a generator expression which does the job of the iterator by "drip feeding" the sum function with x^k values as it iterates over the range (1, j+1). In cases when N (which is j-i) is arbitrarily large, using a standard list can result in huge memory overhead and performance disadvantages. Using a generator expression allows us to avoid these issues, as iterators (which is what generator expressions create) will overwrite the same piece of memory with the new value and only generate the next value when needed.

Of course it only does all this if i <= j else it will return 0.

Lastly, make mistakes and ask questions. The community is great and very helpful

Answer 3

Well, do not use print. It is easy to modify your function like this,

if i<=j:
    s = 0
    for x in range (i, j+1):
        s += x**k
    return s  # print(s) if you really want to
else:
    return 0

Usually functions do not print anything. Instead they return values for their caller to either print or further process. For example, someone may want to find the value of Adder(3, 6, 2)+1, but if you return nothing, they have no way to do this, since the result is not passed to the program. A side note, do not capitalize functions. Those are for classes.

Answer 4

I'm not sure if this is what you want but

if i<=j:
sum = 0
for x in range (i, j+1):
    sum = sum + x**k #sum += x**k for simplicity

this will give you the sum of the powers