Can't convert string to integer under while loop in python

Question

I'm new to python. In this code, I'm trying to ask for numbers repeatedly. When the user enters 0, the program print the average of the numbers exclude 0. I can get the average from this code. However, there's a ValueError,

y = int(input())
ValueError: invalid literal for int() with base 10: ''

I don't understand why this error happens. Is it because of convert variable type under while loop? Can anyone help? Thanks!!

nums=0
i=0
x = int(input())
while x>0:
    y = int(input())
    i = i + 1
    nums = y + nums
    if y == 0:
        avg = (nums+x)/(i)
        print("The average of those numbers is {:.2f}.".format(avg))

Welcome to SO! From the error message, I would deduce that you are typing an extra enter that would be treated as an empty string by the `input` function in the while loop — Hemerson Tacon, Sep 12 '20 at 13:08

score 2 · Answer 1 · answered Sep 12 '20 at 13:08

2

This error occurs when you try to input a string of characters, instead of numbers.

E.g:

if you input '', 'string' - These won't work
but if you input '9', '239412' - This will work

answered Sep 12 '20 at 13:08

Blade

190
4
12

score 0 · Answer 2 · answered Sep 12 '20 at 13:12

It is likely the line y = int(input()) is receiving a string from the user input .
See this example.

>>> while True:
...  y = int(input())
...  print "Y=",y
...
12
Y= 12
0
Y= 0
"this"
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
ValueError: invalid literal for int() with base 10: 'this'

score 0 · Answer 3 · answered Sep 12 '20 at 13:18

Like @Blade said you should give numbers as input. You can do this:

nums=0
i=0
try:
    x = int(input())
    while x>0:
        try:
            y = int(input())
            i = i + 1
            nums = y + nums
            if y == 0:
                avg = (nums+x)/(i)
                print("The average of those numbers is {:.2f}.".format(avg))
        except:
            print("Input is not a number")
        
except:
    print("Input is not a number")

score 0 · Answer 4 · answered Sep 12 '20 at 13:23

You got the Value Error because you entered a space( "") which considered as a string but the input should be an integer int For calculating the average of two numbers you can use this simple code instead : -

def average(x, y):
    " Returns the average of two numbers "
    return (x+y)/2


x = int(input("Enter a number:\n"))
y = int(input("Enter another number :\n"))
print(average(x, y))

Can't convert string to integer under while loop in python

4 Answers4