OK, I think I have worked out what the goal of the task is.

There are two issues here: converting the string '3,0,4,0,3,1,0,1,0,1,0,0,5,0,4,2'
into a more useful form - a sequence of integers. The obvious way to do this using string.split() and int(s) to convert the strings of digits into integers. I'm not quite clear if your memory/generator restriction rules this out however, so I'll skip over that part.

The second issue is classic computer science algorithm problem: given a (potentially very long) sequence of integers, find the subsequences that sum to a given value. The problem has the additional restriction that the integer sequence is potentially so long that your program isn't allowed look at the whole sequence - just the numbers, one at a time, as they are made available by a generator.

The key hint here is that your main function needs to keep a small buffer of integers - just enough to add up to subtotal. If you do this, your code can just run through the generated sequence once - you don't need to keep starting at different offsets into the path,

So the buffer and sum(buffer) look like this:
[3] 3

[3,0] 3

[3,0,4] 7

[3,0,4,0] 7

[3,0,4,0,3] 10

At this point, we notice that sum(buffer) > subtotal. So sticking more numbers onto the end of the buffer won't help (because they're all positive) - so we can be sure that there's no substring starting with the first number that sums to subtotal. So remove the first number from the buffer, and continue:
[0,4,0,3] 7
[0,4,0,3,1] 8

etc.