How to sum a list in python using while loop

Simple use if statement with a while loop to calculate the Sum of n numbers in Python. Taken a number input from the user and stored it in a variable num.

Use a while loop to iterate until num gets zero. In every iteration, add the num to sum, and the value of num is decreased by 1.

Simple example code sum of natural numbers up to num.

num = 15
sum = 0

# use while loop to iterate until zero
while num > 0:
    sum += num
    num -= 1
print("The sum is", sum)

Output:

User input number sum

sum = 0

num = int(input("Enter a number: "))
if num < 0:
    print("Please 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 number: 10
The sum is 55

Do comment if you have any doubts or suggestions on this Python sum topic.

Note: IDE: PyCharm 2021.3.3 (Community Edition)

Windows 10

Python 3.10.1

All Python Examples are in Python 3, so Maybe its different from python 2 or upgraded versions.

Degree in Computer Science and Engineer: App Developer and has multiple Programming languages experience. Enthusiasm for technology & like learning technical.