Find the Sum of Natural Numbers
Course- Python >
Source Code
# Python program to find the sum of natural numbers up to n where n is provided by user
# take input from the user
num = int(input("Enter a number: "))
if num < 0:
print("Enter a positive number")
else:
sum = 0
# use while loop to iterate un till zero
while(num > 0):
sum += num
num -= 1
print("The sum is",sum)
Output
Enter a number: 16 The sum is 136
Here, we ask the user for a number and display the sum of natural numbers up to that number. We use while
loop to iterate until the number becomes zero.
We could have solved the above problem without using any loops. From mathematics, we know that sum of natural numbers is given by n*(n+1)/2
. We could have used this formula directly. For example, if n = 16, the sum would be (16*17)/2 = 136.