How to print only the last result of an array of sum in python

August 24, 2022

I’m resolving a problem, The user input a natural number, and I have to return the final sum of the numbers from 1 to the number in the input, I solved it like this:

     number=int(input("enter a natural number"))
     if number<0: 
         print("The number is not positive") 
     else:   
         n=0   
         for i in range (1,number+1):
             n+=i
             print(n)

For example, if the user puts five, the program should return 15, but I get this:
1
3
6
10
15

How can I make to only receive the answer 15?
Thanks a lot!

>Solution :

You have all the steps because your print statement is in your for loop.
Change it like this:

number = int(input("Enter a positive natural number: "))
if number < 0:
    print("The number needs to be positive")
    exit()  # Stops the program

result = 0
for i in range(1, number + 1):
    result += i

print(result)    # We print after the calculations

There’s also a mathematical alternative (see here):

number = int(input("Enter a positive natural number: "))
if number < 0:
    print("The number needs to be positive")
    exit()  # Stops the program
print(number * (number + 1) / 2)