LiteSpeed Support Forums - Need help with this python script

OK I pretty new to python but I'm pretty sure this should work. everything is defined, only posted whats causing the problem. expression is a Reverse Polish Notation for a calculator (ex 1 2 +) and has already been parsed at this point into single array elements. All I get after running is a SERVER ERROR.

Code:

stack = []

i = 0

j = 0



for i in range(len(expression))

        if len(expression) <= 2

                print "Invalid Expression: Not enough elements"

                break

        if expression[i] == '+' || expression[i] == '-' || expression[i] == '*'

                if i == 0 || i == 1

                        print "Invalid Expression: Operator out of place!"

                        break

                if expression[i] == '+'

                        stack[j-2] = stack[j-2] + stack[j-1]

                        j = j - 1

                        stack[j] = ""

                if expression[i] == '-'

                        stack[j-2] = stack[j-2] - stack[j-1]

                        j = j - 1

                        stack[j] = ""

                if expression[i] == '*'

                        stack[j-2] = stack[j-2] * stack[j-1]

                        j = j - 1

                        stack[j] = ""

        else

                stack[j] = int(expression[i])

                j = j + 1



print stack[0]