Python giving incorrect output when adding 2 values [duplicate]

Question

I am trying to make a calculator program in Python as a bit of a challenge. I am a beginner to python and I am probably making some really obvious mistake. In my calculator I ask the user to define the values and to select the operation they want to use. With the addition operation the calculator gives a strange output. For an example I am telling the calculator to add '7 + 7'. Instead of giving me the correct answer of 14, it gives me 77. Here is my code so far. Hope somebody can help. Cheers

#Sets the values for calculator to use
val1 = input ("Enter the first value: ")
val2 = input ("Enter the second value: ")

#Asks what operation to use
print ("1. Add")
print ("2. Subtract")
print ("3. Divide")
print ("4. Multiply")
op = input ("What operation should I use:")

#Addition
if op == '1':
    print(val1, " + ", val2, " = ", (val1 + val2))

typecast to int

vks
– vks

2019-04-26 22:18:16 +00:00
Commented Apr 26, 2019 at 22:18 — vks
– vks, Commented Apr 26, 2019 at 22:18

Sheldore · Accepted Answer · 2019-04-26 23:01:48Z

2

The user input is of string type. That's why 7 + 7 becomes 77. You need to convert them to integer using int() (or float using float()) type to perform arithmetic

val1 = int(input ("Enter the first value: "))
val2 = int(input ("Enter the second value: "))

As pointed out by @Bailey Parker, in case the user input isn't a number, you can consider using try/except as mentioned here

edited Apr 26, 2019 at 23:01

answered Apr 26, 2019 at 22:18

Sheldore

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3 Comments

SyNC Mutant Over a year ago

This worked, thanks for the help. Will accept answer after the cooldown

Bailey Parker Over a year ago

Note that int and float may raise a ValueError if the thing input isn't a number (ex. int('foo')). You probably want to do this in a try/except wrapped in a while.

Sheldore Over a year ago

@BaileyParker: Thanks for the pointer. I added your suggestion

Paul M. · Accepted Answer · 2019-04-26 22:18:32Z

0

When the + operator's two operands are strings, it will concatenate them together, creating a longer string. You'll need to turn your strings into integers to do math with them.

answered Apr 26, 2019 at 22:18

Paul M.

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