Fastest way to remove first and last lines from a Python string

I have a python script that, for various reasons, has a variable that is a fairly large string, say 10mb long. This string contains multiple lines.

What is the fastest way to remove the first and last lines of this string? Due to the size of the string, the faster the operation, the better; there is an emphasis on speed. The program returns a slightly smaller string, sans the first and last lines.

'\n'.join(string_variable[-1].split('\n')[1:-1]) is the easiest way to do this, but it's extremely slow because the split() function copies the object in memory, and the join() copies it again.

Example string:

*** START OF DATA ***datadatadata*** END OF DATA ***

Extra credit: Have this program not choke if there is no data in between; this is optional, since for my case there shouldn't be a string with no data in between.