Hey guys, in this blog we will see a Python Program to Find the Sum of Natural Numbers.
Example 1: Using While Loop
# Python Program to Find the Sum of Natural Numbers
num = int(input("Enter a positive number -> "))
if num < 0:
print("Enter a positive number")
else:
sum = 0
# use while loop to iterate until zero
while(num > 0):
sum += num
num -= 1
print("The sum is ->", sum)
Output
Enter a positive number -> 4 The sum is -> 10
Enter a positive number -> 5 The sum is -> 15
Enter a positive number -> 6 The sum is -> 21
- In this way, we have simply declared a sum variable and we keep on adding the number to this variable.
- Also simultaneously we are reducing our original number in every iteration.
- Suppose the user inputs 4, our program will add 4 to sum which is currently 0, and reduce our org number 4 to 3, now in the next iteration our program will add 3 to sum, now sum becomes 7 and num becomes 2 and in this way when num becomes 0, our loop will break.
Example 2: Using the formula
sum = n*(n+1)/2
# Sum of natural numbers up to num
num = int(input("Enter a positive number -> "))
if num < 0:
print("Enter a positive number")
else:
sum = (num*(num+1))//2
print("The sum is ->", sum)
Output
Enter a positive number -> 8 The sum is -> 36
Enter a positive number -> 9 The sum is -> 45
Enter a positive number -> 10 The sum is -> 55
- This is the easiest way of calculating the sum of all natural numbers till a positive number.
- Suppose n=8, so the sum of all natural numbers till 8 will be (8*9)/2 which equals 36.
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