What is the sum of the numbers from 1 to N in python ?

 Question Source

We can calculate the sum of numbers from 1 to N by using for loop or by using mathematical formula.

sum of natural numbers = n(n+1)/2

Method 1 (by using for loop) :

Code : 

num = int(input("Input Any Number : "))

sum = 0

for i in range(1,num+1):

    sum += i

print("Sum of",num,"terms is :",sum)

Output :

Input Any Number : 100

Sum of 100 terms is : 5050

Method 2 (by using formula) :

Code :

num = int(input("Input Any Number : "))

sum = int(num*(num+1)/2)

print("Sum of",num,"terms is :",sum)

Output :

Input Any Number : 100

Sum of 100 terms is : 5050

In this method you have to type cast sum variable to integer otherwise the final output will be of the float type i.e. 5050.0