Program to calculate sum of first n natural numbers in Python

In this program we are not using the natural number addition formula n(n+1)/2, instead we are adding the natural numbers using while loop. The user is asked to enter the value of n and then the program calculates the sum of natural numbers upto the entered value n.

# Python program to calculate the sum of n Natural Numbers

# n denotes upto which number you want to calculate the sum
# for example, if n is 5 then the sum of first 5 natural numbers
num = int(input("Enter the value of n: "))
hold = num
sum = 0

if num <= 0: 
   print("Enter a whole positive number!") 
   while num > 0:
        sum = sum + num
        num = num - 1;
    # displaying output
    print("Sum of first", hold, "natural numbers is: ", sum)

Output 1:

Enter the value of n: 6
Sum of first 6 natural numbers is:  21

Output 2:

Enter the value of n: 0
Enter a whole positive number!

Output 3:

Enter the value of n: -10
Enter a whole positive number!

Output 4:

Enter the value of n: 20
Sum of first 20 natural numbers is:  210

Thought of the day-

“Logic will take you from A to B. Imagination will take you everywhere.”- Albert Einstein

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मई जून की गरमी , तापमान 50 डिग्री से ऊपर ऐसे में घर की छत ऐसे तपती है जैसे आग | तपती  छत की गरमी को कम करने के लिए वैसे तो कई उपाय बताए जाते है | लेकिन जो सबसे बेस्ट उपाय है , वो हैं घर की छत पर सफ़ेद पेंट से पुताई | ऐसा करने से आपको इंस्टेंट रिजल्ट ( Instant Result ) मिलते हैं | और गरमी की तपती दुपहरी में छत भी कम तपती है | लेकिन ऐसा आखिर होता क्यूँ है | आज हम को यही बताने जा रहे है की घर की छत पर सफ्र्द पेंट से पुताई करने से आखिर गर्मी कम क्यों हो जाती है |

देश के कई क्षेत्रो में गरमी का प्रकोप बहुत ज्यादा होता है , खासतौर से मिडिल क्लास परिवारों के लिए यह बहुत ही मुश्किलों से भरा दौर होता है |

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