Q:

Splitting input into two with for-loop

This is where I got stuck, trying to learn Python using web-course.

Write a program that takes a single input line of the form «number1»+«number2», where both of these represent positive integers, and outputs the sum of the two numbers. For example on input 5+12 the output should be 17.

We shouldn't use split() or any import.
I think the solution is to use Character and its value of 43 and on that way substring but I am not sure. Only thing that I am sure is that solution is simple no fancy functions or imports needed. 
Here is what i think might be close to solution
S = input()
for position in range(0,len(S):
      #code for substrings 5 to number1, and 12 to number2
result = int(number1)+int(number2)
print(result)

A:

Use str.partition:
line = raw_input()
num1, _, num2 = line.partition('+')
print(int(num1) + int(num2))

If you can't use str.partition and want to use a for loop, then enumerate should help:
for i, c in enumerate(line):
    if c == '+':
        # what goes here?

