Program to compute sum of even and odd numbers received in stream by user

Question

In this particular code I have to find the sum of even and odd number given the by user in stream, as I can observe everything is ok in the code but still not able to run it and getting ValueError: invalid literal for int() with base 10:

sum_of_even_number=0
sum_of_odd_number=0

while True:  # We have created a infinite loop
    user_input=input()
    if user_input=="\n\n":
        break
    num=int(user_input)
    if num % 2==0:
        sum_of_even_number+=num
    else:
        sum_of_odd_number+=num

print("sum_of_even_number :  ",sum_of_even_number)
print("sum_of_odd_number :  ",sum_of_odd_number)

I don't think `user_input=="\n\n"` can ever be true. If the user doesn't enter a number and just presses Enter, the input value will be a blank string, not two carriage returns. — John Gordon, Jul 02 '22 at 17:41
What input is causing the error? If it was nothing, then that could cause the `ValueError`. i.e. `int("")`. Note that `input()` will never return newlines, so testing for that is a waste of time. — martineau, Jul 02 '22 at 17:41
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miistyyy · Answer 1 · 2022-07-02T18:07:33.747

You're getting a Value Error because you are trying to parse an empty string. If the user presses the enter key, then it gets formatted as a string with no text. So instead of checking to see if your text contains \n, check to see if its an empty string or not, like this:

sum_of_even_number=0
sum_of_odd_number=0

while True:  # We have created a infinite loop
    user_input=input()
    if user_input == "":
        break
    num = int(user_input)
    if num % 2 == 0:
        sum_of_even_number += num
    else:
        sum_of_odd_number+=num
        
print("sum_of_even_number :  ",sum_of_even_number)
print("sum_of_odd_number :  ",sum_of_odd_number)

For more help: ValueError: invalid literal for int() with base 10: ''

This doesn't tell even or odd. – toyota Supra Jul 02 '22 at 18:45 — toyota Supra, Jul 02 '22 at 18:45

score 0 · Answer 2 · answered Jul 02 '22 at 19:19

the use of the "isdigit()" method is to prevent value error(if the user enters an alphanumeric value that can not be converted to an int or a float). Although this only works for positive whole numbers due to the "isdigit()" method. I also added a quit option to prevent the loop from being infinite.

sum_odd = 0
sum_even = 0
stat = True #looping condition
while stat:
    num = input("Enter a number or enter q to quit: ")
    if num.isdigit() == True: #to verify if the string is a positive int 
        if int(num)%2 ==0: #checking if the number is even
            sum_even+=int(num)
            print("sum of even number = "+str(sum_even))
        elif int(num)%2 ==1: #checking if the number is odd
            sum_odd+=int(num)
            print("sum of odd number = "+str(sum_odd))
    elif num.lower() == "q": #this breaks the loop 
        stat = False #change of looping condition
print("done") #indicating end of code

sample output:

Enter a number or enter q to quit: 10
sum of even number = 10
Enter a number or enter q to quit: 13
sum of odd number = 13
Enter a number or enter q to quit: 12
sum of even number = 22
Enter a number or enter q to quit: 15
sum of odd number = 28
Enter a number or enter q to quit: 16
sum of even number = 38
Enter a number or enter q to quit: 8
sum of even number = 46
Enter a number or enter q to quit: 9
sum of odd number = 37
Enter a number or enter q to quit: q
done

toyota Supra · Answer 3 · 2022-07-02T18:54:58.500

Edit: Fixing indentation.

Without Walrus operator:

Before: Using same code as your. I put print inside if/else condition block Use the f-string format as well.

sum_of_even_number=0
sum_of_odd_number=0

while True:  # We have created a infinite loop
    user_input=input('Enter number:')
    if user_input=="\n\n":
        break
    num=int(user_input)
    if num % 2==0:
        sum_of_even_number+=num
        print(f"sum_of_even_number : {sum_of_even_number}")
    else:
        sum_of_odd_number+=num
        print(f"sum_of_odd_number :  {sum_of_odd_number}")

With Python 3.8 Walrus Operator:

sum_of_even_number=0
sum_of_odd_number=0

while (user_input := input('Enter number:')):  # We have created a infinite loop
     
    num = int(user_input)
    if num % 2 == 0:
        sum_of_even_number = num
        print(f"sum_of_even_number : {sum_of_even_number}")
    else:
        sum_of_odd_number = num
        print(f"sum_of_odd_number :  {sum_of_odd_number}")

Both output are same.

Enter number:6
sum_of_even_number : 6
Enter number:5
sum_of_odd_number :  5
Enter number:8
sum_of_even_number : 8
Enter number:100
sum_of_even_number : 100
Enter number:105
sum_of_odd_number :  105
Enter number:

Walrus Operator in Python 3.8 You don't need if/else, then break. The Walrus is attempting to avoid being nested if/else. — toyota Supra, Jul 02 '22 at 18:49
The output from this code varies significantly from OP's requirements — DarkKnight, Jul 03 '22 at 20:17

Program to compute sum of even and odd numbers received in stream by user

3 Answers3