Confusing result from raw_input() in Python

Question

I'm having problems with the "operator" variable. So far I have only tried +. It doesn't seem to register and I can't figure out why. i'm using the online python interpreter on repl.it because I'm having problems with my computer.

EDIT: I should probably add that I just started learning Python (I had some Java experience but it was years ago). I'm trying to create a simple text calculator.

    restart=raw_input("to restart calculations enter \'true\'")

    #if restart == "true":
        #stuff

    numone=raw_input("Enter the first number: ")
    operator = raw_input("Enter the operator(+,-,*,/):")
    operator = str(operator)
    numtwo=raw_input("Enter another number: ")
    print("operator: " + operator)

    if operator== '+':
        answer=numone+numtwo
        print(answer)
        print("test")

    if operator == "-":
        answer=numone-numtwo
        print(answer)

    else:
        print("something went wrong")

    #if operator == "*":

What's the problem?... Note that you don't need operator = str(operator). — Maroun
– Maroun, Commented Aug 19, 2014 at 7:28
I guess this is homework? Otherwise why don't you simply use eval? — Emilien
– Emilien, Commented Aug 19, 2014 at 7:34
Its not homework. I'm just starting out and didn't even know about eval lol. I'll look at it. — user2465510
– user2465510, Commented Aug 19, 2014 at 7:37
You could also use a while loop with the raw_input, to test if it is an integer, this way you always get integer values with the input. — W1ll1amvl
– W1ll1amvl, Commented Aug 19, 2014 at 7:39

Maroun · Accepted Answer · 2014-08-19 07:31:12Z

3

Your problem is that you're concatenating two strings, you should cast to int before:

answer = int(numone) + int(numtwo)

Why? Because raw_input reads the input as string.

answered Aug 19, 2014 at 7:31

Maroun

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Comments

sundar nataraj · Accepted Answer · 2014-08-19 07:35:22Z

Give elif to the second statement

since user give '+'

first if statment excutes but in next statement it fails and go to the else so for + you get two result both addition and something wrong

and also you need to convert the operands to integer

one more thing while converting to integer you need check right conditions for integer else it will give error

numone=raw_input("Enter the first number: ")
operator = raw_input("Enter the operator(+,-,*,/):")
operator = str(operator)
numtwo=raw_input("Enter another number: ")
print("operator: " + operator)

if operator== '+':
    try:        
        answer=int(numone)+int(numtwo)
        print(answer)
        print("test")
    except  ValueError:
        print "one of the operand is not integer"

elif operator == "-":
    try:
       answer=int(numone)-int(numtwo)
       print(answer)
       print("test")
    except  ValueError:
       print "one of the operand is not integer"        

else:
    print("something went wrong")

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