Capturing the positions of "start" and "end" markers in a multi-line string
If you are certain that there is exactly one match, then you don't need to iterate.  You could write:

start, end = re.search('start.*ends?', sstring, re.DOTALL).span()


To note:


Take advantage of re.DOTALL so that the regex can span multiple lines.
Use match.span() and destructuring assignment to get both the start and end in one statement.
The [s]? after start is, from a mechanical viewpoint, useless.  You might want to keep it just for symmetry.


The spacing in print (something) is kind of weird; print(something) would be more conventional.