re.sub do not replace portion of match

[J Wolfe]

Hi,

Is there a way to flag re.sub not to replace a portion of the string?

I have a very long string that I want to add two new line's to rather
than one, but keep the value X:

string = "test........X.\n.today"  <-- note X is a value
string = re.sub("test........X.\n.","test........X.\n\n.", string)

This just replaces X with the replacement string.

Thanks,
Jonathan