[Tutor] Parsing text file

[Alan]

I'm looking for a more elegant way to parse sections of text files that 
are bordered by BEGIN/END delimiting phrases, like this:

some text
some more text
BEGIN_INTERESTING_BIT
someline1
someline2
someline3
END_INTERESTING_BIT
more text
more text

What I have been doing is clumsy, involving converting to a string and 
slicing out the required section using split('DELIMITER'): 

import sys
infile = open(sys.argv[1], 'r')
#join list elements with @ character into a string
fileStr = '@'.join(infile.readlines())
#Slice out the interesting section with split, then split again into 
lines using @
resultLine = 
fileStr.split('BEGIN_INTERESTING_BIT')[1].split('END_INTERESTING_BIT')[0].split('@')
for line in resultLine:
    do things

Can anyone point me at a better way to do this?

Thanks

-- 
--------------------------
Alan Wardroper
alan at wardroper.org