Correct syntax for pathological re.search()

I'm trying to discard lines that include the string "\sout{" (which is TeX, for
those who are curious. I have tried:
   if not re.search("\sout{", line):
   if not re.search("\sout\{", line):
   if not re.search("\sout{", line):
   if not re.search("\sout\{", line):
But the lines with that string keep coming through. What is the right syntax to
properly escape the backslash and the left curly bracket?
--
Michael F. Stemper
No animals were harmed in the composition of this message.