more troubles with my program

[the_2nd_coming]

thank-you for all the help you have given this newbie, not only to python 
but also programming.

I am still having troubles with my program, it tells me that I am trying to 
apply a mathematical operator to non integers.

hear is my source:
------------------------------------------------------------------
def evaluate(list):
        num1 = list[0]
        num2 = list[2]
        operator = list[1]
        print num1
        print num2
        if operator == '+':
                answer = num1 + num2
        elif operator == '-':
                answer = num1 - num2
        elif operator == 'X':
                answer = num1 * num2
        elif operator == 'x':
                answer = num1 * num2
        elif operator == '*':
                answer = num1 * num2
        elif operator == '/':
                answer = num1 / num2
        else:
                print 'invalid operator'
        
def fix_expression(list):
        word = list
        print word
        l = []
        n1 = word[0]
        n2 = word[1]
        n3 = word[2]
        l.append(n1)
        l.append(n2)
        l.append(n3)
        evaluate(l)
        
# - - - - - - - - - - - - - - - -  - - - - - - - - - - - - - - - - - - - - 
- - - - - - - - - - - - - - - - - - - - - 
import string
expression = raw_input('please enter your singel operator expression')
string.strip(expression) # get rid of all leading and trailing white space#
list = string.split(expression)

if len(list) >1:
        print evaluate(list)
elif len(list) == 1:
        print fix_expression(list[0])
         
else:
        import sys
        sys.exit

-------------------------------------------------------------------------------

could it be due to the fact that I use raw_input?
I would think that once you take a number out of a character string you 
should be able to perform math functions on it. am I wrong?

thanks

J.