Python, get sum of a list of numbers with recursion

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I want to sum numbers with a recursive function, i.e.

getSum([1, 2, 3, 4, 5]) 

should return 1+2+3+4+5 == 15

I'm not an expert in recursive functions, I've tried something like:

def getSum(piece):
    for i in piece
        suc += getSum(i)

The problem is that I can't loop through integers. I'm sure this is a quite easy task but I really can't figure it out.

You don't need to loop. Recursion will do that for you.

def getSum(piece):
    if len(piece)==0:
        return 0
    else:
        return piece[0] + getSum(piece[1:]) 
print getSum([1, 3, 4, 2, 5])

Python, get sum of a list of numbers with recursion, Suppose that you want to calculate the sum of a list of numbers such as: [1,3,5,7,​9]. How can we take this idea and turn it into a Python program? First Figure 1 shows the series of recursive calls that are needed to sum the list [1,3,5,7,9]. Python Program to Find Sum of Natural Numbers Using Recursion Python Program to Find Sum of Natural Numbers Using Recursion In this program, you'll learn to find the sum of natural numbers using recursive function. To understand this example, you should have the knowledge of the following Python programming topics:

I think it is a little nicer without explicitly checking the length:

def getSum(piece):
    return piece[0] + getSum(piece[1:]) if piece else 0

Demo:

>>> getSum([1, 2, 3, 4, 5])
15

5.3. Calculating the Sum of a List of Numbers, Suppose that you want to calculate the sum of a list of numbers such as: [1,3,5,7,​9]. First, let's restate the sum problem in terms of Python lists. We might Figure 1 shows the series of recursive calls that are needed to sum the list [1,3,5,​7,9]. Python Exercises, Practice and Solution: Write a Python program of recursion list sum.

For academic purposes (learning Python) you could use recursion:

def getSum(iterable):
    if not iterable:
        return 0  # End of recursion
    else:
        return iterable[0] + getSum(iterable[1:])  # Recursion step

But you shouldn't use recursion in real production code. It's not efficient and the code much less clear then with using built-ins. For this case you do not need neither recursion nor loop. Just use built-in sum:

>>>a = [1, 2, 3, 4, 5]
>>>sum(a) 
15

Calculating the Sum of a List of Numbers, Given a list of numbers, write a Python program to find the sum of all the elements in the list. Example: to find sum of all. # elements in list using recursion. Calculating the Sum of a List of Numbers¶ We will begin our investigation with a simple problem that you already know how to solve without using recursion. Suppose that you want to calculate the sum of a list of numbers such as: \([1, 3, 5, 7, 9]\) .

You can use reduce also. The function reduce(func, seq) continually applies the function func() to the sequence seq. It returns a single value.

reduce(lambda x,y: x+y, range(1,6))

Sum of array elements using recursion, In the program below, we've used a recursive function recur_sum() to compute the sum up to the given number. Source Code. # Python program to find the sum of  Calculating the Sum of a List of Numbers¶ We will begin our investigation with a simple problem that you already know how to solve without using recursion. Suppose that you want to calculate the sum of a list of numbers such as: \([1, 3, 5, 7, 9]\) .

Or, in a more "Pythonic" way:

suml = lambda l: l[0] + suml(l[1:]) if l else 0

print(suml(range(101)))
Output: 5050

Python program to find sum of elements in list, Next: Write a Python program to get the factorial of a non-negative integer. What is the difficulty level of this exercise? Easy Medium Hard. Test  So the line return sum(n)+sum(n-1) is incorrect; it needs to be n plus the sum of the n - 1 other values. This also makes sense as that's what you want to compute. You need to return a value for the base case and for the recursive case. As such you can simplify your code to: def sum(n): if n == 0: return 0 return n + sum(n - 1)

Python Program to Find Sum of Natural Numbers Using Recursion, The formula seems to be: for each [i][j] take the sum of the row right to [i][j] and the column down from [i][j]. Both sums start with the element at  Using recursion to sum numbers. a recursive Sum method looks like this: Recursive number summing program returning “None” as the sum in Python. 114.

Programming in Python - List sum using recursion, Given an array of integers, find sum of array elements using recursion. We have discussed iterative solution in below post. In this post, recursive solution is discussed. // elements using recursion. // elements using recursion. # elements using recursion. // elements using recursion. // A [0..N-1] using recursion.

Python Data Structures and Algorithms, Python includes a sum function for lists. The default Python implementation, CPython, uses an indefinite for-loop in C to create those functions (source code here for those interested). Let's see how to do it with recursion: The base case is the empty list - the best sum for that is 0.

Comments
  • And what if I want to check sum after every call of function getSum?So I wanna check f.e. if sum>9: do something ?
  • But I have to do it with recursion :P
  • Don't do it with recursion in production code. For academic purposes it could be OK, but don't dot it in real life.
  • uselpa, Thanks, fixed.