Python: adding numbers

Question

Why does

import sys

class k:
    x = int(sys.argv[1])
    y = int(sys.argv[2])
    z = 0

def add():
        k.z = k.x + k.y

def main():   
    add()
    print  (k.z)

if __name__ == "__main__" : main()

Give me 10 when I use the number 5 and 5 at command, and

class k:
x = 0
y = 0
z = 0
def add():
    k.z  = k.x + k.y

def main():   
    k.x = input("Enter a number")
    k.y = input("Enter another number")    
    add()
    print  (k.z)

if __name__ == "__main__" : main()

Gives me 55 when I enter 5 and 5 on the prompts.

Thanks in advance.

FWIW, in Python, it's usual practice to create an instance of a class & work with that, rather than working directly with the class and manipulating class attributes like your code does. Of course, one wouldn't normally even bother using a class for something simple like this, except as a learning exercise. For further info please see Class Objects in the official Python tutorial. — PM 2Ring
– PM 2Ring, Commented Aug 30, 2015 at 7:56

ZdaR · Accepted Answer · 2015-08-30 07:42:22Z

1

In the second example, you forgot yo typecast the input to int, since the input() returns a str object and the + operator concatenates the strings.

def main():   
    k.x = int(input("Enter a number"))
    k.y = int(input("Enter another number"))    
    add()

edited Aug 30, 2015 at 7:42

answered Aug 30, 2015 at 7:41

ZdaR

23.1k7 gold badges70 silver badges90 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

le_camerone Over a year ago

Thank your very much! So even if I declare that the values are 'int' originally I have to declare again that the value coming in is an 'int' when I go to the input step?

Tony Suffolk 66 Over a year ago

You don't declare variables in Python. In your code you set them to integers, but they are just names which point to values and the name can be pointed to other values regardless of their type at any time in your code without any warning.

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

Because on your second example, both x and y are strings (so '5'+'5' = '55')

To fix this:

def main():   
    value = input("Enter a number")
    k.x = int(value)

    value = input("Enter another number")
    k.y = int(value) 

    add()
    print  (k.z)

edited Jun 20, 2020 at 9:12

CommunityBot

11 silver badge

answered Aug 30, 2015 at 7:39

Jossef Harush Kadouri

34.6k10 gold badges143 silver badges133 bronze badges

1 Comment

le_camerone Over a year ago

Thanks for your reply.

Collectives™ on Stack Overflow

Python: adding numbers

2 Answers 2

2 Comments

To fix this:

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

To fix this:

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related